It would, so to speak, appear as an accident, when to a thing that could exist alone on its own account, subsequently a state of affairs could be made to fit. If things can occur in atomic facts, this possibility must already lie in them. (A logical entity cannot be merely possible. Logic treats of every possibility, and all possibilities are its facts.) Just as we cannot think of spatial objects at all apart from space, or temporal objects apart from time, so we cannot think of any object apart from the possibility of its connexion with other things.

The thing is independent, in so far as it can occur in all possible circumstances, but this form of independence is a form of connexion with the atomic fact, a form of dependence. (It is impossible for words to occur in two different ways, alone and in the proposition.)

If I know an object, then I also know all the possibilities of its occurrence in atomic facts. (Every such possibility must lie in the nature of the object.) A new possibility cannot subsequently be found.

A spatial object must lie in infinite space. (A point in space is an argument place.) A speck in a visual field need not be red, but it must have a colour; it has, so to speak, a colour space round it. A tone must have a pitch, the object of the sense of touch a hardness, etc.

Every statement about complexes can be analysed into a statement about their constituent parts, and into those propositions which completely describe the complexes.

The substance of the world can only determine a form and not any material properties. For these are first presented by the propositions—first formed by the configuration of the objects.

Either a thing has properties which no other has, and then one can distinguish it straight away from the others by a description and refer to it; or, on the other hand, there are several things which have the totality of their properties in common, and then it is quite impossible to point to any one of them. For if a thing is not distinguished by anything, I cannot distinguish it—for otherwise it would be distinguished.

The existence and non-existence of atomic facts is the reality. (The existence of atomic facts we also call a positive fact, their non-existence a negative fact.)

That the elements of the picture are combined with one another in a definite way, represents that the things are so combined with one another. This connexion of the elements of the picture is called its structure, and the possibility of this structure is called the form of representation of the picture.

What the picture must have in common with reality in order to be able to represent it after its manner—rightly or falsely—is its form of representation.

The picture represents its object from without (its standpoint is its form of representation), therefore the picture represents its object rightly or falsely.

What every picture, of whatever form, must have in common with reality in order to be able to represent it at all—rightly or falsely—is the logical form, that is, the form of reality.

It used to be said that God could create everything, except what was contrary to the laws of logic. The truth is, we could not say of an “unlogical” world how it would look.

To present in language anything which “contradicts logic” is as impossible as in geometry to present by its co-ordinates a figure which contradicts the laws of space; or to give the co-ordinates of a point which does not exist.

We use the sensibly perceptible sign (sound or written sign, etc.) of the proposition as a projection of the possible state of affairs. The method of projection is the thinking of the sense of the proposition.

The sign through which we express the thought I call the propositional sign. And the proposition is the propositional sign in its projective relation to the world.

To the proposition belongs everything which belongs to the projection; but not what is projected. Therefore the possibility of what is projected but not this itself. In the proposition, therefore, its sense is not yet contained, but the possibility of expressing it. (“The content of the proposition” means the content of the significant proposition.) In the proposition the form of its sense is contained, but not its content.

That the propositional sign is a fact is concealed by the ordinary form of expression, written or printed. For in the printed proposition, for example, the sign of a proposition does not appear essentially different from a word. (Thus it was possible for Frege to call the proposition a compounded name.)

The essential nature of the propositional sign becomes very clear when we imagine it made up of spatial objects (such as tables, chairs, books) instead of written signs. The mutual spatial position of these things then expresses the sense of the proposition.

We must not say, “The complex sign ‘aRb’ says ‘a stands in relation R to b’”; but we must say, “That ‘a’ stands in a certain relation to ‘b’ says that aRb”.

Objects I can only name. Signs represent them. I can only speak of them. I cannot assert them. A proposition can only say how a thing is, not what it is.

A proposition about a complex stands in internal relation to the proposition about its constituent part. A complex can only be given by its description, and this will either be right or wrong. The proposition in which there is mention of a complex, if this does not exist, becomes not nonsense but simply false. That a propositional element signifies a complex can be seen from an indeterminateness in the propositions in which it occurs.

Every defined sign signifies via those signs by which it is defined, and the definitions show the way. Two signs, one a primitive sign, and one defined by primitive signs, cannot signify in the same way. Names cannot be taken to pieces by definition (nor any sign which alone and independently has a meaning).

The meanings of primitive signs can be explained by elucidations. Elucidations are propositions which contain the primitive signs. They can, therefore, only be understood when the meanings of these signs are already known.

Every part of a proposition which characterizes its sense I call an expression (a symbol). (The proposition itself is an expression.) Expressions are everything—essential for the sense of the proposition—that propositions can have in common with one another. An expression characterizes a form and a content.

It is therefore represented by the general form of the propositions which it characterizes. And in this form the expression is constant and everything else variable.

An expression is thus presented by a variable, whose values are the propositions which contain the expression. (In the limiting case the variable becomes constant, the expression a proposition.) I call such a variable a “propositional variable”.

If we change a constituent part of a proposition into a variable, there is a class of propositions which are all the values of the resulting variable proposition. This class in general still depends on what, by arbitrary agreement, we mean by parts of that proposition. But if we change all those signs, whose meaning was arbitrarily determined, into variables, there always remains such a class. But this is now no longer dependent on any agreement; it depends only on the nature of the proposition.

The determination of the values of the propositional variable is done by indicating the propositions whose common mark the variable is. The determination is a description of these propositions. The determination will therefore deal only with symbols not with their meaning. And only this is essential to the determination, that it is only a description of symbols and asserts nothing about what is symbolized. The way in which we describe the propositions is not essential.

It can never indicate the common characteristic of two objects that we symbolize them with the same signs but by different methods of symbolizing. For the sign is arbitrary. We could therefore equally well choose two different signs and where then would be what was common in the symbolization?

In the language of everyday life it very often happens that the same word signifies in two different ways—and therefore belongs to two different symbols—or that two words, which signify in different ways, are apparently applied in the same way in the proposition. Thus the word “is” appears as the copula, as the sign of equality, and as the expression of existence; “to exist” as an intransitive verb like “to go”; “identical” as an adjective; we speak of something but also of the fact of something happening.

In order to avoid these errors, we must employ a symbolism which excludes them, by not applying the same sign in different symbols and by not applying signs in the same way which signify in different ways. A symbolism, that is to say, which obeys the rules of logical grammar—of logical syntax. (The logical symbolism of Frege and Russell is such a language, which, however, does still not exclude all errors.

If a sign is not necessary then it is meaningless. That is the meaning of Occam’s razor. (If everything in the symbolism works as though a sign had meaning, then it has meaning.)

In logical syntax the meaning of a sign ought never to play a rôle; it must admit of being established without mention being thereby made of the meaning of a sign; it ought to presuppose only the description of the expressions.

From this observation we get a further view—into Russell’s Theory of Types. Russell’s error is shown by the fact that in drawing up his symbolic rules he has to speak about the things his signs mean.

A function cannot be its own argument, because the functional sign already contains the prototype of its own argument and it cannot contain itself. If, for example, we suppose that the function F(fx) could be its own argument, then there would be a proposition “F(F(fx))”, and in this the outer function F and the inner function F must have different meanings; for the inner has the form φ(fx), the outer the form ψ(φ(fx)).

A proposition possesses essential and accidental features. Accidental are the features which are due to a particular way of producing the propositional sign. Essential are those which alone enable the proposition to express its sense.

The essential in a proposition is therefore that which is common to all propositions which can express the same sense. And in the same way in general the essential in a symbol is that which all symbols which can fulfill the same purpose have in common.

One could therefore say the real name is that which all symbols, which signify an object, have in common. It would then follow, step by step, that no sort of composition was essential for a name.

In our notations there is indeed something arbitrary, but this is not arbitrary, namely that if we have determined anything arbitrarily, then something else must be the case. (This results from the essence of the notation.)

A particular method of symbolizing may be unimportant, but it is always important that this is a possible method of symbolizing. And this happens as a rule in philosophy: The single thing proves over and over again to be unimportant, but the possibility of every single thing reveals something about the nature of the world.

Definitions are rules for the translation of one language into another. Every correct symbolism must be translatable into every other according to such rules. It is this which all have in common.

We can, for example, express what is common to all notations for the truth-functions as follows: It is common to them that they all, for example, can be replaced by the notations of “~p” (“not p”) and “p∨q” (“p or q”). (Herewith is indicated the way in which a special possible notation can give us general information.)

The sign of the complex is not arbitrarily resolved in the analysis, in such a way that its resolution would be different in every propositional structure.

The proposition determines a place in logical space: the existence of this logical place is guaranteed by the existence of the constituent parts alone, by the existence of the significant proposition.

Although a proposition may only determine one place in logical space, the whole logical space must already be given by it. (Otherwise denial, the logical sum, the logical product, etc., would always introduce new elements—in co-ordination.) (The logical scaffolding round the picture determines the logical space. The proposition reaches through the whole logical space.)

Man possesses the capacity of constructing languages, in which every sense can be expressed, without having an idea how and what each word means—just as one speaks without knowing how the single sounds are produced. Colloquial language is a part of the human organism and is not less complicated than it. From it it is humanly impossible to gather immediately the logic of language. Language disguises the thought; so that from the external form of the clothes one cannot infer the form of the thought they clothe, because the external form of the clothes is constructed with quite another object than to let the form of the body be recognized.

Most propositions and questions, that have been written about philosophical matters, are not false, but senseless. We cannot, therefore, answer questions of this kind at all, but only state their senselessness. Most questions and propositions of the philosophers result from the fact that we do not understand the logic of our language. (They are of the same kind as the question whether the Good is more or less identical than the Beautiful.

All philosophy is “Critique of language” (but not at all in Mauthner’s sense). Russell’s merit is to have shown that the apparent logical form of the proposition need not be its real form.

At the first glance the proposition—say as it stands printed on paper—does not seem to be a picture of the reality of which it treats. But nor does the musical score appear at first sight to be a picture of a musical piece; nor does our phonetic spelling (letters) seem to be a picture of our spoken language. And yet these symbolisms prove to be pictures—even in the ordinary sense of the word—of what they represent.

And if we penetrate to the essence of this pictorial nature we see that this is not disturbed by apparent irregularities (like the use of ♯ and ♭ in the score). For these irregularities also picture what they are to express; only in another way.

The gramophone record, the musical thought, the score, the waves of sound, all stand to one another in that pictorial internal relation, which holds between language and the world. To all of them the logical structure is common. (Like the two youths, their two horses and their lilies in the story. They are all in a certain sense one.)

In the fact that there is a general rule by which the musician is able to read the symphony out of the score, and that there is a rule by which one could reconstruct the symphony from the line on a gramophone record and from this again—by means of the first rule—construct the score, herein lies the internal similarity between these things which at first sight seem to be entirely different.

In order to understand the essence of the proposition, consider hieroglyphic writing, which pictures the facts it describes. And from it came the alphabet without the essence of the representation being lost.

The proposition is a picture of reality, for I know the state of affairs presented by it, if I understand the proposition. And I understand the proposition, without its sense having been explained to me.

The proposition determines reality to this extent, that one only needs to say “Yes” or “No” to it to make it agree with reality. Reality must therefore be completely described by the proposition. A proposition is the description of a fact. As the description of an object describes it by its external properties so propositions describe reality by its internal properties. The proposition constructs a world with the help of a logical scaffolding, and therefore one can actually see in the proposition all the logical features possessed by reality if it is true.

To understand a proposition means to know what is the case, if it is true. (One can therefore understand it without knowing whether it is true or not.) One understands it if one understands it constituent parts.

The translation of one language into another is not a process of translating each proposition of the one into a proposition of the other, but only the constituent parts of propositions are translated. (And the dictionary does not only translate substantives but also adverbs and conjunctions, etc., and it treats them all alike.)

A proposition must communicate a new sense with old words. The proposition communicates to us a state of affairs, therefore it must be essentially connected with the state of affairs. And the connexion is, in fact, that it is its logical picture. The proposition only asserts something, in so far as it is a picture.

In the proposition a state of affairs is, as it were, put together for the sake of experiment. One can say, instead of, This proposition has such and such a sense, This proposition represents such and such a state of affairs.

One name stands for one thing, and another for another thing, and they are connected together. And so the whole, like a living picture, presents the atomic fact.

The possibility of propositions is based upon the principle of the representation of objects by signs. My fundamental thought is that the “logical constants” do not represent. That the logic of the facts cannot be represented.

The proposition is a picture of its state of affairs, only in so far as it is logically articulated. (Even the proposition “ambulo” is composite, for its stem gives a different sense with another termination, or its termination with another stem.)

In the proposition there must be exactly as many thing distinguishable as there are in the state of affairs, which it represents. They must both possess the same logical (mathematical) multiplicity (cf. Hertz’s Mechanics, on Dynamic Models).

If we tried, for example, to express what is expressed by “(x).fx” by putting an index before fx, like: “Gen. fx”, it would not do, we should not know what was generalized. If we tried to show it by an index g, like: “f(xg)” it would not do—we should not know the scope of the generalization. If we were to try it by introducing a mark in the argument places, like “(G, G).

For the same reason the idealist explanation of the seeing of spatial relations through “spatial spectacles” does not do, because it cannot explain the multiplicity of these relations.

If one does not observe that propositions have a sense independent of the facts, one can easily believe that true and false are two relations between signs and things signified with equal rights. One could, then, for example, say that “p” signifies in the true way what “~p” signifies in the false way, etc.

Can we not make ourselves understood by means of false propositions as hitherto with true ones, so long as we know that they are meant to be false? No! For a proposition is true, if what we assert by means of it is the case; and if by “p” we mean ~p, and what we mean is the case, then “p” in the new conception is true and not false.

That, however, the signs “p” and “~p” can say the same thing is important, for it shows that the sign “~” corresponds to nothing in reality. That negation occurs in a proposition, is no characteristic of its sense (~~p=p). The propositions “p” and “~p” have opposite senses, but to them corresponds one and the same reality.

An illustration to explain the concept of truth. A black spot on white paper; the form of the spot can be described by saying of each point of the plane whether it is white or black. To the fact that a point is black corresponds a positive fact; to the fact that a point is white (not black), a negative fact. If I indicate a point of the plane (a truth-value in Frege’s terminology), this corresponds to the assumption proposed for judgment, etc.

Every proposition must already have a sense; assertion cannot give it a sense, for what it asserts is the sense itself. And the same holds of denial, etc.

One could say, the denial is already related to the logical place determined by the proposition that is denied. The denying proposition determines a logical place other than does the proposition denied. The denying proposition determines a logical place, with the help of the logical place of the proposition denied, by saying that it lies outside the latter place. That one can deny again the denied proposition, shows that what is denied is already a proposition and not merely the preliminary to a proposition.

Philosophy is not one of the natural sciences. (The word “philosophy” must mean something which stands above or below, but not beside the natural sciences.)

The object of philosophy is the logical clarification of thoughts. Philosophy is not a theory but an activity. A philosophical work consists essentially of elucidations. The result of philosophy is not a number of “philosophical propositions”, but to make propositions clear. Philosophy should make clear and delimit sharply the thoughts which otherwise are, as it were, opaque and blurred.

Psychology is no nearer related to philosophy, than is any other natural science. The theory of knowledge is the philosophy of psychology. Does not my study of sign-language correspond to the study of thought processes which philosophers held to be so essential to the philosophy of logic? Only they got entangled for the most part in unessential psychological investigations, and there is an analogous danger for my method.

Propositions can represent the whole reality, but they cannot represent what they must have in common with reality in order to be able to represent it—the logical form. To be able to represent the logical form, we should have to be able to put ourselves with the propositions outside logic, that is outside the world.

Propositions cannot represent the logical form: this mirrors itself in the propositions. That which mirrors itself in language, language cannot represent. That which expresses itself in language, we cannot express by language. The propositions show the logical form of reality. They exhibit it.

Thus a proposition “fa” shows that in its sense the object a occurs, two propositions “fa” and “ga” that they are both about the same object. If two propositions contradict one another, this is shown by their structure; similarly if one follows from another, etc.

We can speak in a certain sense of formal properties of objects and atomic facts, or of properties of the structure of facts, and in the same sense of formal relations and relations of structures. (Instead of property of the structure I also say “internal property”; instead of relation of structures “internal relation”. I introduce these expressions in order to show the reason for the confusion, very widespread among philosophers, between internal relations and proper (external) relations.

A property is internal if it is unthinkable that its object does not possess it. (This bright blue colour and that stand in the internal relation of bright and darker eo ipso. It is unthinkable that these two objects should not stand in this relation.) (Here to the shifting use of the words “property” and “relation” there corresponds the shifting use of the word “object”.)

The existence of an internal property of a possible state of affairs is not expressed by a proposition, but it expresses itself in the proposition which presents that state of affairs, by an internal property of this proposition. It would be as senseless to ascribe a formal property to a proposition as to deny it the formal property.

One cannot distinguish forms from one another by saying that one has this property, the other that: for this assumes that there is a sense in asserting either property of either form.

The existence of an internal relation between possible states of affairs expresses itself in language by an internal relation between the propositions presenting them.

Series which are ordered by internal relations I call formal series. The series of numbers is ordered not by an external, but by an internal relation. Similarly the series of propositions “aRb”, “(∃x):aRx.xRb”, “(∃x,y):aRx.xRy.yRb”, etc. (If b stands in one of these relations to a, I call b a successor of a.)

In the sense in which we speak of formal properties we can now speak also of formal concepts. (I introduce this expression in order to make clear the confusion of formal concepts with proper concepts which runs through the whole of the old logic.) That anything falls under a formal concept as an object belonging to it, cannot be expressed by a proposition. But it is shown in the symbol for the object itself.

Every variable is the sign of a formal concept. For every variable presents a constant form, which all its values possess, and which can be conceived as a formal property of these values.

So the variable name “x” is the proper sign of the pseudo-concept object. Wherever the word “object” (“thing”, “entity”, etc.) is rightly used, it is expressed in logical symbolism by the variable name. For example in the proposition “there are two objects which …”, by “(∃x,y)…”. Wherever it is used otherwise, i.e. as a proper concept word, there arise senseless pseudo-propositions. So one cannot, e.g. say “There are objects” as one says “There are books”.

The formal concept is already given with an object, which falls under it. One cannot, therefore, introduce both, the objects which fall under a formal concept and the formal concept itself, as primitive ideas. One cannot, therefore, e.g. introduce (as Russell does) the concept of function and also special functions as primitive ideas; or the concept of number and definite numbers.

If we want to express in logical symbolism the general proposition “b is a successor of a” we need for this an expression for the general term of the formal series:

The question about the existence of a formal concept is senseless. For no proposition can answer such a question. (For example, one cannot ask: “Are there unanalysable subject-predicate propositions?”)

It is obvious that in the analysis of propositions we must come to elementary propositions, which consist of names in immediate combination. The question arises here, how the propositional connexion comes to be.

Even if the world is infinitely complex, so that every fact consists of an infinite number of atomic facts and every atomic fact is composed of an infinite number of objects, even then there must be objects and atomic facts.

The names are the simple symbols, I indicate them by single letters (x, y, z). The elementary proposition I write as function of the names, in the form “fx”, “φ(x,y)”, etc. Or I indicate it by the letters p, q, r.

If I use two signs with one and the same meaning, I express this by putting between them the sign “=”. “a=b” means then, that the sign “a” is replaceable by the sign “b”. (If I introduce by an equation a new sign “b”, by determining that it shall replace a previously known sign “a”, I write the equation—definition—(like Russell) in the form “a=b Def.”. A definition is a symbolic rule.

Can we understand two names without knowing whether they signify the same thing or two different things? Can we understand a proposition in which two names occur, without knowing if they mean the same or different things? If I know the meaning of an English and a synonymous German word, it is impossible for me not to know that they are synonymous, it is impossible for me not to be able to translate them into one another.

The specification of all true elementary propositions describes the world completely. The world is completely described by the specification of all elementary propositions plus the specification, which of them are true and which false.

With regard to the existence of n atomic facts there are Kn = n(nν)∑ν = 0 possibilities. It is possible for all combinations of atomic facts to exist, and the others not to exist.

The truth-possibilities can be presented by schemata of the following kind (“T” means “true”, “F” “false”. The rows of T’s and F’s under the row of the elementary propositions mean their truth-possibilities in an easily intelligible symbolism).

It seems probable even at first sight that the introduction of the elementary propositions is fundamental for the comprehension of the other kinds of propositions. Indeed the comprehension of the general propositions depends palpably on that of the elementary propositions.

With regard to the agreement and disagreement of a proposition with the truth-possibilities of n elementary propositions there are Kn(Knκ) = Ln∑κ = 0 possibilities.

Agreement with the truth-possibilities can be expressed by co-ordinating with them in the schema the mark “T” (true). Absence of this mark means disagreement.

The expression of the agreement and disagreement with the truth-possibilities of the elementary propositions expresses the truth-conditions of the proposition. The proposition is the expression of its truth-conditions. (Frege has therefore quite rightly put them at the beginning, as explaining the signs of his logical symbolism. Only Frege’s explanation of the truth-concept is false: if “the true” and “the false” were real objects and the arguments in ~p, etc., then the sense of ~p would by no means be determined by Frege’s determination.

It is clear that to the complex of the signs “F” and “T” no object (or complex of objects) corresponds; any more than to horizontal and vertical lines or to brackets. There are no “logical objects”. Something analogous holds of course for all signs, which express the same as the schemata of “T” and “F”.

Thus e.g.
(Frege’s assertion sign “⊢” is logically altogether meaningless; in Frege (and Russell) it only shows that these authors hold as true the propositions marked in this way. “⊢” belongs therefore to the propositions no more than does the number of the proposition. A proposition cannot possibly assert of itself that it is true.) If the sequence of the truth-possibilities in the schema is once for all determined by a rule of combination, then the last column is by itself an expression of the truth-conditions.

For n elementary propositions there are Ln possible groups of truth-conditions. The groups of truth-conditions which belong to the truth-possibilities of a number of elementary propositions can be ordered in a series.

Among the possible groups of truth-conditions there are two extreme cases. In the one case the proposition is true for all the truth-possibilities of the elementary propositions. We say that the truth-conditions are tautological. In the second case the proposition is false for all the truth-possibilities. The truth-conditions are self-contradictory. In the first case we call the proposition a tautology, in the second case a contradiction.

The proposition shows what it says, the tautology and the contradiction that they say nothing. The tautology has no truth-conditions, for it is unconditionally true; and the contradiction is on no condition true. Tautology and contradiction are without sense. (Like the point from which two arrows go out in opposite directions.) (I know, e.g. nothing about the weather, when I know that it rains or does not rain.)

Tautology and contradiction are, however, not nonsensical; they are part of the symbolism, in the same way that “0” is part of the symbolism of Arithmetic.

Tautology and contradiction are not pictures of the reality. They present no possible state of affairs. For the one allows every possible state of affairs, the other none. In the tautology the conditions of agreement with the world—the presenting relations—cancel one another, so that it stands in no presenting relation to reality.

The truth-conditions determine the range, which is left to the facts by the proposition. (The proposition, the picture, the model, are in a negative sense like a solid body, which restricts the free movement of another: in a positive sense, like the space limited by solid substance, in which a body may be placed.) Tautology leaves to reality the whole infinite logical space; contradiction fills the whole logical space and leaves no point to reality.

The truth of tautology is certain, of propositions possible, of contradiction impossible. (Certain, possible, impossible: here we have an indication of that gradation which we need in the theory of probability.)

The logical product of a tautology and a proposition says the same as the proposition. Therefore that product is identical with the proposition. For the essence of the symbol cannot be altered without altering its sense.

To a definite logical combination of signs corresponds a definite logical combination of their meanings; every arbitrary combination only corresponds to the unconnected signs. That is, propositions which are true for every state of affairs cannot be combinations of signs at all, for otherwise there could only correspond to them definite combinations of objects. (And to no logical combination corresponds no combination of the objects.) Tautology and contradiction are the limiting cases of the combination of symbols, namely their dissolution.

Of course the signs are also combined with one another in the tautology and contradiction, i.e. they stand in relations to one another, but these relations are meaningless, unessential to the symbol.

Now it appears to be possible to give the most general form of proposition; i.e. to give a description of the propositions of some one sign language, so that every possible sense can be expressed by a symbol, which falls under the description, and so that every symbol which falls under the description can express a sense, if the meanings of the names are chosen accordingly. It is clear that in the description of the most general form of proposition only what is essential to it may be described—otherwise it would not be the most general form.

Suppose all elementary propositions were given me: then we can simply ask: what propositions I can build out of them. And these are all propositions and so are they limited.

The propositions are everything which follows from the totality of all elementary propositions (of course also from the fact that it is the totality of them all). (So, in some sense, one could say, that all propositions are generalizations of the elementary propositions.)

It is natural to confuse the arguments of functions with the indices of names. For I recognize the meaning of the sign containing it from the argument just as much as from the index. In Russell’s “+c”, for example, “c” is an index which indicates that the whole sign is the addition sign for cardinal numbers. But this way of symbolizing depends on arbitrary agreement, and one could choose a simple sign instead of “+c”: but in “~p” “p” is not an index but an argument; the sense of “~p” cannot be understood, unless the sense of “p” has previously been understood.

The truth-functions of every number of elementary propositions can be written in a schema of the following kind:
Those truth-possibilities of its truth-arguments, which verify the proposition, I shall call its truth-grounds.

If the truth-grounds which are common to a number of propositions are all also truth-grounds of some one proposition, we say that the truth of this proposition follows from the truth of those propositions.

In particular the truth of a proposition p follows from that of a proposition q, if all the truth-grounds of the second are truth-grounds of the first.

If a god creates a world in which certain propositions are true, he creates thereby also a world in which all propositions consequent on them are true. And similarly he could not create a world in which the proposition “p” is true without creating all its objects.

“p.q” is one of the propositions which assert “p” and at the same time one of the propositions which assert “q”. Two propositions are opposed to one another if there is no significant proposition which asserts them both. Every proposition which contradicts another, denies it.

If the truth of one proposition follows from the truth of others, this expresses itself in relations in which the forms of these propositions stand to one another, and we do not need to put them in these relations first by connecting them with one another in a proposition; for these relations are internal, and exist as soon as, and by the very fact that, the propositions exist.

When we conclude from p∨q and ~p to q the relation between the forms of the propositions “p∨q” and “~p” is here concealed by the method of symbolizing. But if we write, e.g. instead of “p∨q” “p|q.|.p|q” and instead of “~p” “p|p” (p|q = neither p nor q), then the inner connexion becomes obvious. (The fact that we can infer fa from (x).fx shows that generality is present also in the symbol “(x).

If p follows from q, I can conclude from q to p; infer p from q. The method of inference is to be understood from the two propositions alone. Only they themselves can justify the inference. Laws of inference, which—as in Frege and Russell—are to justify the conclusions, are senseless and would be superfluous.

The freedom of the will consists in the fact that future actions cannot be known now. We could only know them if causality were an inner necessity, like that of logical deduction.—The connexion of knowledge and what is known is that of logical necessity. (“A knows that p is the case” is senseless if p is a tautology.)

If from the fact that a proposition is obvious to us it does not follow that it is true, then obviousness is no justification for our belief in its truth.

Contradiction is something shared by propositions, which no proposition has in common with another. Tautology is that which is shared by all propositions, which have nothing in common with one another. Contradiction vanishes so to speak outside, tautology inside all propositions. Contradiction is the external limit of the propositions, tautology their substanceless centre.

If Tr is the number of the truth-grounds of the proposition “r”, Trs the number of those truth-grounds of the proposition “s” which are at the same time truth-grounds of “r”, then we call the ratio Trs : Tr the measure of the probability which the proposition “r” gives to the proposition “s”.

Suppose in a schema like that above in No. 5.101 Tr is the number of the “T” ’s in the proposition r, Trs the number of those “T” ’s in the proposition s, which stand in the same columns as “T” ’s of the proposition r; then the proposition r gives to the proposition s the probability Trs : Tr.

Propositions which have no truth-arguments in common with one another we call independent. Independent propositions (e.g. any two elementary propositions) give to one another the probability ½. If p follows from q, the proposition q gives to the proposition p the probability 1. The certainty of logical conclusion is a limiting case of probability. (Application to tautology and contradiction.)

In an urn there are equal numbers of white and black balls (and no others). I draw one ball after another and put them back in the urn. Then I can determine by the experiment that the numbers of the black and white balls which are drawn approximate as the drawing continues. So this is not a mathematical fact. If then, I say, It is equally probable that I should draw a white and a black ball, this means, All the circumstances known to me (including the natural laws hypothetically assumed) give to the occurrence of the one event no more probability than to the occurrence of the other.

The unit of the probability proposition is: The circumstances—with which I am not further acquainted—give to the occurrence of a definite event such and such a degree of probability.

Probability is a generalization. It involves a general description of a propositional form. Only in default of certainty do we need probability. If we are not completely acquainted with a fact, but know something about its form. (A proposition can, indeed, be an incomplete picture of a certain state of affairs, but it is always a complete picture.) The probability proposition is, as it were, an extract from other propositions.

We can bring out these internal relations in our manner of expression, by presenting a proposition as the result of an operation which produces it from other propositions (the bases of the operation).

The first place in which an operation can occur is where a proposition arises from another in a logically significant way; i.e. where the logical construction of the proposition begins.

The truth-functions of elementary proposition, are results of operations which have the elementary propositions as bases. (I call these operations, truth-operations.)

The sense of a truth-function of p is a function of the sense of p. Denial, logical addition, logical multiplication, etc., etc., are operations. (Denial reverses the sense of a proposition.)

An operation shows itself in a variable; it shows how we can proceed from one form of proposition to another. It gives expression to the difference between the forms. (And that which is common the the bases, and the result of an operation, is the bases themselves.)

The same operation which makes “q” from “p”, makes “r” from “q”, and so on. This can only be expressed by the fact that “p”, “q”, “r”, etc., are variables which give general expression to certain formal relations.

The occurrence of an operation does not characterize the sense of a proposition. For an operation does not assert anything; only its result does, and this depends on the bases of the operation. (Operation and function must not be confused with one another.)

Only in this way is the progress from term to term in a formal series possible (from type to type in the hierarchy of Russell and Whitehead). (Russell and Whitehead have not admitted the possibility of this progress but have made use of it all the same.)

The repeated application of an operation to its own result I call its successive application (“O’O’O’a” is the result of the threefold successive application of “O’ξ” to “a”). In a similar sense I speak of the successive application of several operations to a number of propositions.

The general term of the formal series a, O’a, O’O’a,…. I write thus: “[a, x, O’x]”. This expression in brackets is a variable. The first term of the expression is the beginning of the formal series, the second the form of an arbitrary term x of the series, and the third the form of that term of the series which immediately follows x.

All propositions are results of truth-operations on the elementary propositions. The truth-operation is the way in which a truth-function arises from elementary propositions. According to the nature of truth-operations, in the same way as out of elementary propositions arise their truth-functions, from truth-functions arises a new one. Every truth-operation creates from truth-functions of elementary propositions, another truth-function of elementary propositions i.e. a proposition. The result of every truth-operation on the results of truth-operations on elementary propositions is also the result of one truth-operation on elementary propositions.

The Schemata No. 4.31 are also significant, if “p”, “q”, “r”, etc. are not elementary propositions. And it is easy to see that the propositional sign in No. 4.442 expresses one truth-function of elementary propositions even when “p” and “q” are truth-functions of elementary propositions.

That ∨, ⊃, etc., are not relations in the sense of right and left, etc., is obvious. The possibility of crosswise definition of the logical “primitive signs” of Frege and Russell shows by itself that these are not primitive signs and that they signify no relations. And it is obvious that the “⊃” which we define by means of “~” and “∨” is identical with that by which we define “∨” with the help of “~”, and that this “∨” is the same as the first, and so on.

That from a fact p an infinite number of others should follow, namely, ~~p, ~~~~p, etc., is indeed hardly to be believed, and it is no less wonderful that the infinite number of propositions of logic (of mathematics) should follow from half a dozen “primitive propositions”. But the propositions of logic say the same thing. That is, nothing.

Truth-functions are not material functions. If e.g. an affirmation can be produced by repeated denial, is the denial—in any sense—contained in the affirmation? Does “~~p” deny ~p, or does it affirm p; or both? The proposition “~~p” does not treat of denial as an object, but the possibility of denial is already prejudged in affirmation. And if there was an object called “~”, then “~~p” would have to say something other than “p”.

If there are logical primitive signs a correct logic must make clear their position relative to one another and justify their existence. The construction of logic out of its primitive signs must become clear.

If logic has primitive ideas these must be independent of one another. If a primitive idea is introduced it must be introduced in all contexts in which it occurs at all. One cannot therefore introduce it for one context and then again for another. For example, if denial is introduced, we must understand it in propositions of the form “~p”, just as in propositions like “~(p∨q)”, “(∃x).~fx” and others. We may not first introduce it for one class of cases and then for another, for it would then remain doubtful whether its meaning in the two cases was the same, and there would be no reason to use the same way of symbolizing in the two cases.

The introduction of a new expedient in the symbolism of logic must always be an event full of consequences. No new symbol may be introduced in logic in brackets or in the margin—with, so to speak, an entirely innocent face. (Thus in the “Principia Mathematica” of Russell and Whitehead there occur definitions and primitive propositions in words. Why suddenly words here? This would need a justification. There was none, and can be none for the process is actually not allowed.

All numbers in logic must be capable of justification. Or rather it must become plain that there are no numbers in logic. There are no pre-eminent numbers.

The solution of logical problems must be neat for they set the standard of neatness. Men have always thought that there must be a sphere of questions whose answers—a priori—are symmetrical and united into a closed regular structure. A sphere in which the proposition, simplex sigillum veri, is valid.

When we have rightly introduced the logical signs, the sense of all their combinations has been already introduced with them: therefore not only “p∨q” but also “~(p∨~q)”, etc. etc. We should then already have introduced the effect of all possible combinations of brackets; and it would then have become clear that the proper general primitive signs are not “p∨q”, “(∃x).fx”, etc., but the most general form of their combinations.

The apparently unimportant fact that the apparent relations like ∨ and ⊃ need brackets—unlike real relations—is of great importance. The use of brackets with these apparent primitive signs shows that these are not the real primitive signs; and nobody of course would believe that the brackets have meaning by themselves.

It is clear that everything which can be said beforehand about the form of all propositions at all can be said on one occasion. For all logical operations are already contained in the elementary proposition. For “fa” says the same as

Logic must take care of itself. A possible sign must also be able to signify. Everything which is possible in logic is also permitted. (“Socrates is identical” means nothing because there is no property which is called “identical”. The proposition is senseless because we have not made some arbitrary determination, not because the symbol is in itself unpermissible.) In a certain sense we cannot make mistakes in logic.

Self-evidence, of which Russell has said so much, can only be discard in logic by language itself preventing every logical mistake. That logic is a priori consists in the fact that we cannot think illogically.

Occam’s razor is, of course, not an arbitrary rule nor one justified by its practical success. It simply says that unnecessary elements in a symbolism mean nothing. Signs which serve one purpose are logically equivalent, signs which serve no purpose are logically meaningless.

Frege says: Every legitimately constructed proposition must have a sense; and I say: Every possible proposition is legitimately constructed, and if it has no sense this can only be because we have given no meaning to some of its constituent parts. (Even if we believe that we have done so.) Thus “Socrates is identical” says nothing, because we have given no meaning to the word “identical” as adjective. For when it occurs as the sign of equality it symbolizes in an entirely different way—the symbolizing relation is another—therefore the symbol is in the two cases entirely different; the two symbols have the sign in common with one another only by accident.

Every truth-function is a result of the successive application of the operation (−−−−−T) (ξ, . . . . .) to elementary propositions. This operation denies all the propositions in the right-hand bracket and I call it the negation of these propositions.

An expression in brackets whose terms are propositions I indicate—if the order of the terms in the bracket is indifferent—by a sign of the form “(ξ)”. “ξ” is a variable whose values are the terms of the expression in brackets, and the line over the variable indicates that it stands for all its values in the bracket. (Thus if ξ has the 3 values P, Q, R, then (ξ)=(P, Q, R).

As it is obviously easy to express how propositions can be constructed by means of this operation and how propositions are not to be constructed by means of it, this must be capable of exact expression.

How can the all-embracing logic which mirrors the world use such special catches and manipulations? Only because all these are connected into an infinitely fine network, to the great mirror.

“~p” is true if “p” is false. Therefore in the true proposition “~p” “p” is a false proposition. How then can the stroke “~” bring it into agreement with reality? That which denies in “~p” is however not “~”, but that which all signs of this notation, which deny p, have in common. Hence the common rule according to which “~p”, “~~~p”, “~p∨~p”, “~p.~p”, etc. etc. (to infinity) are constructed. And this which is common to them all mirrors denial.

We could say: What is common to all symbols, which assert both p and q, is the proposition “p.q”. What is common to all symbols, which asserts either p or q, is the proposition “p∨q”. And similarly we can say: Two propositions are opposed to one another when they have nothing in common with one another; and every proposition has only one negative, because there is only one proposition which lies altogether outside it.

If a notation is fixed, there is in it a rule according to which all the propositions denying p are constructed, a rule according to which all the propositions asserting p are constructed, a rule according to which all the propositions asserting p or q are constructed, and so on. These rules are equivalent to the symbols and in them their sense is mirrored.

It must be recognized in our symbols that what is connected by “∨”, “.”, etc., must be propositions. And this is the case, for the symbols “p” and “q” presuppose “∨”, “~”, etc. If the sign “p” in “p∨q” does not stand for a complex sign, then by itself it cannot have sense; but then also the signs “p∨p”, “p.p”, etc. which have the same sense as “p” have no sense.

Must the sign of the negative proposition be constructed by means of the sign of the positive? Why should one not be able to express the negative proposition by means of a negative fact? (Like: if “a” does not stand in a certain relation to “b”, it could express that aRb is not the case.) But here also the negative proposition is indirectly constructed with the positive. The positive proposition must presuppose the existence of the negative proposition and conversely.

I separate the concept all from the truth-function. Frege and Russell have introduced generality in connexion with the logical product or the logical sum. Then it would be difficult to understand the propositions “(∃x).fx” and “(x).fx” in which both ideas lie concealed.

That which is peculiar to the “symbolism of generality” is firstly, that it refers to a logical prototype, and secondly, that it makes constants prominent.

If the objects are given, therewith are all objects also given. If the elementary propositions are given, then therewith all elementary propositions are also given.

It is not correct to render the proposition “(∃x).fx”—as Russell does—in the words “fx is possible”. Certainty, possibility or impossibility of a state of affairs are not expressed by a proposition but by the fact that an expression is a tautology, a significant proposition or a contradiction. That precedent to which one would always appeal, must be present in the symbol itself.

One can describe the world completely by completely generalized propositions, i.e. without from the outset co-ordinating any name with a definite object. In order then to arrive at the customary way of expression we need simply say after an expression “there is one and only one x, which …”: and this x is a.

A completely generalized proposition is like every other proposition composite. (This is shown by the fact that in “(∃x, φ).φx” we must mention “φ” and “x” separately. Both stand independently in signifying relations to the world as in the ungeneralized proposition.) A characteristic of a composite symbol: it has something in common with other symbols.

The truth or falsehood of every proposition alters something in the general structure of the world. And the range which is allowed to its structure by the totality of elementary propositions is exactly that which the completely general propositions delimit. (If an elementary proposition is true, then, at any rate, there is one more elementary proposition true.)

That identity is not a relation between objects is obvious. This becomes very clear if, for example, one considers the proposition “(x):fx.⊃.x=a”. What this proposition says is simply that only a satisfies the function f, and not that only such things satisfy the function f which have a certain relation to a. One could of course say that in fact only a has this relation to a, but in order to express this we should need the sign of identity itself.

Russell’s definition of “=” won’t do; because according to it one cannot say that two objects have all their properties in common. (Even if this proposition is never true, it is nevertheless significant.)

Roughly speaking: to say of two things that they are identical is nonsense, and to say of one thing that it is identical with itself is to say nothing.

And analogously: not “(∃x,y).f(x,y).x=y”, but “(∃x).f(x,x)”; and not “(∃x,y).f(x,y).~x=y”, but “(∃x,y).f(x,y)”. (Therefore instead of Russell’s “(∃x,y). f(x,y)”: “(∃x,y).f(x,y).∨.(∃x).f(x,x)”.)

Instead of “(x):fx⊃x=a” we therefore write e.g. “(∃x).fx.⊃.fa:~(∃x,y).fx.fy”. And if the proposition “only one x satisfies f( )” reads: “(∃x).fx:~(∃x,y).fx.fy”.

And we see that the apparent propositions like: “a=a”, “a=b.b=c.⊃a=c”, “(x).x=x”. “(∃x).x=a”, etc. cannot be written in a correct logical notation at all.

So all problems disappear which are connected with such pseudo-propositions. This is the place to solve all the problems with arise through Russell’s “Axiom of Infinity”. What the axiom of infinity is meant to say would be expressed in language by the fact that there is an infinite number of names with different meanings.

There are certain cases in which one is tempted to use expressions of the form “a=a” or “p⊃p”. As, for instance, when one would speak of the archetype Proposition, Thing, etc. So Russell in the Principles of Mathematics has rendered the nonsense “p is a proposition” in symbols by “p⊃p” and has put it as hypothesis before certain propositions to show that their places for arguments could only be occupied by propositions.

Similarly it was proposed to express “There are no things” by “~(∃x).x=x”. But even if this were a proposition—would it not be true if indeed “There were things”, but these were not identical with themselves?

At first sight it appears as if there were also a different way in which one proposition could occur in another. Especially in certain propositional forms of psychology, like “A thinks, that p is the case”, or “A thinks p”, etc. Here it appears superficially as if the proposition p stood to the object A in a kind of relation. (And in modern epistemology (Russell, Moore, etc.) those propositions have been conceived in this way.

But it is clear that “A believes that p”, “A thinks p”, “A says p”, are of the form “‘p’ says p”: and here we have no co-ordination of a fact and an object, but a co-ordination of facts by means of a co-ordination of their objects.

This shows that there is no such thing as the soul—the subject, etc.—as it is conceived in superficial psychology. A composite soul would not be a soul any longer.

The correct explanation of the form of the proposition “A judges p” must show that it is impossible to judge a nonsense. (Russell’s theory does not satisfy this condition.)

To perceive a complex means to perceive that its constituents are combined in such and such a way. This perhaps explains that the figure
(If I fix my eyes first on the corners a and only glance at b, a appears in front and b behind, and vice versa.)

We must now answer a priori the question as to all possible forms of the elementary propositions. The elementary proposition consists of names. Since we cannot give the number of names with different meanings, we cannot give the composition of the elementary proposition.

Our fundamental principle is that every question which can be decided at all by logic can be decided off-hand. (And if we get into a situation where we need to answer such a problem by looking at the world, this shows that we are on a fundamentally wrong track.)

The “experience” which we need to understand logic is not that such and such is the case, but that something is; but that is no experience. Logic precedes every experience—that something is so. It is before the How, not before the What.

And if this were not the case, how could we apply logic? We could say: if there were a logic, even if there were no world, how then could there be a logic, since there is a world?

Russell said that there were simple relations between different numbers of things (individuals). But between what numbers? And how should this be decided—by experience? (There is no pre-eminent number.)

May we then ask this at all? Can we set out a sign form and not know whether anything can correspond to it? Has the question sense: what must there be in order that anything can be the case?

It is clear that we have a concept of the elementary proposition apart from its special logical form. Where, however, we can build symbols according to a system, there this system is the logically important thing and not the single symbols. And how would it be possible that I should have to deal with forms in logic which I can invent: but I must have to deal with that which makes it possible for me to invent them.

Empirical reality is limited by the totality of objects. The boundary appears again in the totality of elementary propositions. The hierarchies are and must be independent of reality.

If we know on purely logical grounds, that there must be elementary propositions, then this must be known by everyone who understands propositions in their unanalysed form.

All propositions of our colloquial language are actually, just as they are, logically completely in order. That simple thing which we ought to give here is not a model of the truth but the complete truth itself. (Our problems are not abstract but perhaps the most concrete that there are.)

The application of logic decides what elementary propositions there are. What lies in its application logic cannot anticipate. It is clear that logic may not conflict with its application. But logic must have contact with its application. Therefore logic and its application may not overlap one another.

Logic fills the world: the limits of the world are also its limits. We cannot therefore say in logic: This and this there is in the world, that there is not. For that would apparently presuppose that we exclude certain possibilities, and this cannot be the case since otherwise logic must get outside the limits of the world: that is, if it could consider these limits from the other side also.

This remark provides a key to the question, to what extent solipsism is a truth. In fact what solipsism means, is quite correct, only it cannot be said, but it shows itself. That the world is my world, shows itself in the fact that the limits of the language (the language which I understand) mean the limits of my world.

The thinking, presenting subject; there is no such thing. If I wrote a book “The world as I found it”, I should also have therein to report on my body and say which members obey my will and which do not, etc. This then would be a method of isolating the subject or rather of showing that in an important sense there is no subject: that is to say, of it alone in this book mention could not be made.

Where in the world is a metaphysical subject to be noted? You say that this case is altogether like that of the eye and the field of sight. But you do not really see the eye. And from nothing in the field of sight can it be concluded that it is seen from an eye.

This is connected with the fact that no part of our experience is also a priori. Everything we see could also be otherwise. Everything we describe at all could also be otherwise. There is no order of things a priori.

Here we see that solipsism strictly carried out coincides with pure realism. The I in solipsism shrinks to an extensionless point and there remains the reality co-ordinated with it.

There is therefore really a sense in which the philosophy we can talk of a non-psychological I. The I occurs in philosophy through the fact that the “world is my world”. The philosophical I is not the man, not the human body or the human soul of which psychology treats, but the metaphysical subject, the limit—not a part of the world.

If we are given the general form of the way in which a proposition is constructed, then thereby we are also given the general form of the way in which by an operation out of one proposition another can be created.

The general form of the operation Ω’(η) is therefore: [ξ, N(ξ)]’ (η) (=[η, ξ, N(ξ)]). This is the most general form of transition from one proposition to another.

The concept number is nothing else than that which is common to all numbers, the general form of a number. The concept number is the variable number. And the concept of equality of numbers is the general form of all special equalities of numbers.

The theory of classes is altogether superfluous in mathematics. This is connected with the fact that the generality which we need in mathematics is not the accidental one.

Theories which make a proposition of logic appear substantial are always false. One could e.g. believe that the words “true” and “false” signify two properties among other properties, and then it would appear as a remarkable fact that every proposition possesses one of these properties. This now by no means appears self-evident, no more so than the proposition “All roses are either yellow or red” would seem even if it were true.

It is the characteristic mark of logical propositions that one can perceive in the symbol alone that they are true; and this fact contains in itself the whole philosophy of logic. And so also it is one of the most important facts that the truth or falsehood of non-logical propositions can not be recognized from the propositions alone.

The fact that the propositions of logic are tautologies shows the formal—logical—properties of language, of the world. That its constituent parts connected together in this way give a tautology characterizes the logic of its constituent parts. In order that propositions connected together in a definite way may give a tautology they must have definite properties of structure. That they give a tautology when so connected shows therefore that they possess these properties of structure.

That e.g. the propositions “p” and “~p” in the connexion “~(p.~p)” give a tautology shows that they contradict one another. That the propositions “p⊃q”, “p” and “q” connected together in the form “(p⊃q).(p):⊃:(q)” give a tautology shows that q follows from p and p⊃q. That “(x).fx:⊃:fa” is a tautology shows that fa follows from (x).fx, etc. etc.

In order to recognize a tautology as such, we can, in cases in which no sign of generality occurs in the tautology, make use of the following intuitive method: I write instead of “p”, “q”, “r”, etc., “T p F”, “T q F”, “T r F”, etc. The truth-combinations I express by brackets, e.g.:

The propositions of logic demonstrate the logical properties of propositions, by combining them into propositions which say nothing. This method could be called a zero-method. In a logical proposition propositions are brought into equilibrium with one another, and the state of equilibrium then shows how these propositions must be logically constructed.

Whence it follows that we can get on without logical propositions, for we can recognize in an adequate notation the formal properties of the propositions by mere inspection.

If for example two propositions “p” and “q” give a tautology in the connexion “p⊃q”, then it is clear that q follows from p. E.g. that “q” follows from “p⊃q.p” we see from these two propositions themselves, but we can also show it by combining them to “p⊃q.p:⊃:q” and then showing that this is a tautology.

This throws light on the question why logical propositions can no more be empirically confirmed than they can be empirically refuted. Not only must a proposition of logic be incapable of being contradicted by any possible experience, but it must also be incapable of being confirmed by any such.

It now becomes clear why we often feel as though “logical truths” must be “postulated” by us. We can in fact postulate them in so far as we can postulate an adequate notation.

It is clear that the laws of logic cannot themselves obey further logical laws. (There is not, as Russell supposed, for every “type” a special law of contradiction; but one is sufficient, since it is not applied to itself.)

The mark of logical propositions is not their general validity. To be general is only to be accidentally valid for all things. An ungeneralized proposition can be tautologous just as well as a generalized one.

Logical general validity, we could call essential as opposed to accidental general validity, e.g. of the proposition “all men are mortal”. Propositions like Russell’s “axiom of reducibility” are not logical propositions, and this explains our feeling that, if true, they can only be true by a happy chance.

We can imagine a world in which the axiom of reducibility is not valid. But it is clear that logic has nothing to do with the question whether our world is really of this kind or not.

The logical propositions describe the scaffolding of the world, or rather they present it. They “treat” of nothing. They presuppose that names have meaning, and that elementary propositions have sense. And this is their connexion with the world. It is clear that it must show something about the world that certain combinations of symbols—which essentially have a definite character—are tautologies. Herein lies the decisive point. We said that in the symbols which we use something is arbitrary, something not.

Whether a proposition belongs to logic can be calculated by calculating the logical properties of the symbol. And this we do when we prove a logical proposition. For without troubling ourselves about a sense and a meaning, we form the logical propositions out of others by mere symbolic rules. We prove a logical proposition by creating it out of other logical propositions by applying in succession certain operations, which again generate tautologies out of the first.

It would be too remarkable, if one could prove a significant proposition logically from another, and a logical proposition also. It is clear from the beginning that the logical proof of a significant proposition and the proof in logic must be two quite different things.

The significant proposition asserts something, and its proof shows that it is so; in logic every proposition is the form of a proof. Every proposition of logic is a modus ponens presented in signs. (And the modus ponens can not be expressed by a proposition.)

All propositions of logic are of equal rank; there are not some which are essentially primitive and others deduced from there. Every tautology itself shows that it is a tautology.

It is clear that the number of “primitive propositions of logic” is arbitrary, for we could deduce logic from one primitive proposition by simply forming, for example, the logical produce of Frege’s primitive propositions. (Frege would perhaps say that this would no longer be immediately self-evident. But it is remarkable that so exact a thinker as Frege should have appealed to the degree of self-evidence as the criterion of a logical proposition.

In life it is never a mathematical proposition which we need, but we use mathematical propositions only in order to infer from propositions which do not belong to mathematics to others which equally do not belong to mathematics. (In philosophy the question “Why do we really use that word, that proposition?” constantly leads to valuable results.)

If two expressions are connected by the sign of equality, this means that they can be substituted for one another. But whether this is the case must show itself in the two expressions themselves. It characterizes the logical form of two expressions, that they can be substituted for one another.

Frege says that these expressions have the same meaning but different senses. But what is essential about equation is that it is not necessary in order to show that both expressions, which are connected by the sign of equality, have the same meaning: for this can be perceived from the two expressions themselves.

And, that the propositions of mathematics can be proved means nothing else than that their correctness can be seen without our having to compare what they express with the facts as regards correctness.

The identity of the meaning of two expressions cannot be asserted. For in order to be able to assert anything about their meaning, I must know their meaning, and if I know their meaning, I know whether they mean the same or something different.

To the question whether we need intuition for the solution of mathematical problems it must be answered that language itself here supplies the necessary intuition.

The essential of mathematical method is working with equations. On this method depends the fact that every proposition of mathematics must be self-evident.

The method by which mathematics arrives at its equations is the method of substitution. For equations express the substitutability of two expressions, and we proceed from a number of equations to new equations, replacing expressions by others in accordance with the equations.

The so-called law of induction cannot in any case be a logical law, for it is obviously a significant proposition.—And therefore it cannot be a law a priori either.

“Law of Causality” is a class name. And as in mechanics there are, for instance, minimum-laws, such as that of least actions, so in physics there are causal laws, laws of the causality form.

Men had indeed an idea that there must be a “law of least action”, before they knew exactly how it ran. (Here, as always, the a priori certain proves to be something purely logical.)

All propositions, such as the law of causation, the law of continuity in nature, the law of least expenditure in nature, etc. etc., all these are a priori intuitions of possible forms of the propositions of science.

Newtonian mechanics, for example, brings the description of the universe to a unified form. Let us imagine a white surface with irregular black spots. We now say: Whatever kind of picture these make I can always get as near as I like to its description, if I cover the surface with a sufficiently fine square network and now say of every square that it is white or black. In this way I shall have brought the description of the surface to a unified form.

And now we see the relative position of logic and mechanics. (We could construct the network out of figures of different kinds, as out of triangles and hexagons together.) That a picture like that instanced above can be described by a network of a given form asserts nothing about the picture. (For this holds of every picture of this kind.) But this does characterize the picture, the fact, namely, that it can be completely described by a definite net of definite fineness.

We must not forget that the description of the world by mechanics is always quite general. There is, for example, never any mention of particular material points in it, but always only of some points or other.

Although the spots in our picture are geometrical figures, geometry can obviously say nothing about their actual form and position. But the network is purely geometrical, and all its properties can be given a priori. Laws, like the law of causation, etc., treat of the network and not what the network describes.

We cannot compare any process with the “passage of time”—there is no such thing—but only with another process (say, with the movement of the chronometer). Hence the description of the temporal sequence of events is only possible if we support ourselves on another process. It is exactly analogous for space. When, for example, we say that neither of two events (which mutually exclude one another) can occur, because there is no cause why the one should occur rather than the other, it is really a matter of our being unable to describe one of the two events unless there is some sort of asymmetry.

The Kantian problem of the right and left hand which cannot be made to cover one another already exists in the plane, and even in one-dimensional space; where the two congruent figures a and b cannot be made to cover one another without
A right-hand glove could be put on a left hand if it could be turned round in four-dimensional space.

This process, however, has no logical foundation but only a psychological one. It is clear that there are no grounds for believing that the simplest course of events will really happen.

So people stop short at natural laws as something unassailable, as did the ancients at God and Fate. And they are both right and wrong. but the ancients were clearer, in so far as they recognized one clear terminus, whereas the modern system makes it appear as though everything were explained.

Even if everything we wished were to happen, this would only be, so to speak, a favour of fate, for there is no logical connexion between will and world, which would guarantee this, and the assumed physical connexion itself we could not again will.

For two colours, e.g. to be at one place in the visual field, is impossible, logically impossible, for it is excluded by the logical structure of colour. Let us consider how this contradiction presents itself in physics. Somewhat as follows: That a particle cannot at the same time have two velocities, i.e. that at the same time it cannot be in two places, i.e. that particles in different places at the same time cannot be identical.

The sense of the world must lie outside the world. In the world everything is as it is and happens as it does happen. In it there is no value—and if there were, it would be of no value. If there is a value which is of value, it must lie outside all happening and being-so. For all happening and being-so is accidental. What makes it non-accidental cannot lie in the world, for otherwise this would again be accidental.

The first thought in setting up an ethical law of the form “thou shalt …” is: And what if I do not do it? But it is clear that ethics has nothing to do with punishment and reward in the ordinary sense. This question as to the consequences of an action must therefore be irrelevant. At least these consequences will not be events. For there must be something right in that formulation of the question.

If good or bad willing changes the world, it can only change the limits of the world, not the facts; not the things that can be expressed in language. In brief, the world must thereby become quite another, it must so to speak wax or wane as a whole. The world of the happy is quite another than that of the unhappy.

Death is not an event of life. Death is not lived through. If by eternity is understood not endless temporal duration but timelessness, then he lives eternally who lives in the present. Our life is endless in the way that our visual field is without limit.

The temporal immortality of the human soul, that is to say, its eternal survival also after death, is not only in no way guaranteed, but this assumption in the first place will not do for us what we always tried to make it do. Is a riddle solved by the fact that I survive for ever? Is this eternal life not as enigmatic as our present one? The solution of the riddle of life in space and time lies outside space and time.

The contemplation of the world sub specie aeterni is its contemplation as a limited whole. The feeling that the world is a limited whole is the mystical feeling.

For an answer which cannot be expressed the question too cannot be expressed. The riddle does not exist. If a question can be put at all, then it can also be answered.

Scepticism is not irrefutable, but palpably senseless, if it would doubt where a question cannot be asked. For doubt can only exist where there is a question; a question only where there is an answer, and this only where something can be said.

We feel that even if all possible scientific questions be answered, the problems of life have still not been touched at all. Of course there is then no question left, and just this is the answer.

The solution of the problem of life is seen in the vanishing of this problem. (Is not this the reason why men to whom after long doubting the sense of life became clear, could not then say wherein this sense consisted?)

The right method of philosophy would be this: To say nothing except what can be said, i.e. the propositions of natural science, i.e. something that has nothing to do with philosophy: and then always, when someone else wished to say something metaphysical, to demonstrate to him that he had given no meaning to certain signs in his propositions. This method would be unsatisfying to the other—he would not have the feeling that we were teaching him philosophy—but it would be the only strictly correct method.

My propositions are elucidatory in this way: he who understands me finally recognizes them as senseless, when he has climbed out through them, on them, over them. (He must so to speak throw away the ladder, after he has climbed up on it.) He must surmount these propositions; then he sees the world rightly.