FROM: CRITICAL THEORY SINCE 1965, ed. Hazard Adams & Leroy Searle (Talahassee: Florida State University Press, 1986), pp. 623-36. APPENDIX Gottlob Frege 1848-1925 623 GOTTLOB FREGE, born six years before the death of F. W. Schelling, was for most of his professional life a professor of philosophy at the University of Jena. But unlike his more illustrious predecessors there (including Fichte, Hegel, and Schelling), Frege remained little known and evidently little read during his lifetime. Most of his major philosophical works focused scrupulously, if not to say relentlessly, on mathematical logic. His Begriffsschrift, eine der arithmetischen nachgebildete (1879) is arguably the first important work in the development of modern symbolic logic, and in this work Frege developed a remarkably expressive formalism for representing logical propositions and judgments. While generally neglected, his reputation and influence (especially among English-speaking philosophers) has grown steadily since Russell and Whitehead acknowledged his pioneering efforts in the formalization of logic. Ironically, Frege had an important, albeit indirect, influence on the development of modern European philosophy in his penetrating (and somewhat scathing) critique of Edmund Husserl's Philosophy of Arithmetic (1891). Husserl's response to Frege's critique (according to Joseph Kockelmans) was at least to abandon the psychologism in the book, to which Frege had objected; but this took Husserl in the direction of transcendental psychology and phenomenology- surely not a response that Frege would have approved. In Husserl's later attempt to make philosophy into a rigorous science, the entire matter of representation and expression is subsumed under the notion of a cognitive or perceptual intention, presuming that anything cognizable (including cognition itself) must immediately appear to consciousness as present. While in itself this contrast between Frege and Husserl may be only incidental, it indicates a fundamental conflict in the development of modern critical and philosophical thought. In rejecting transcendental metaphysics and both nominalist and formalist accounts of logic and mathematics, Frege narrowed his philosophical alternatives but radically clarified the importance of language and logic for all philosophical issues. First, he made it clear that how any term orproposition is understood is not necessarily the same as its use to designate some thing or entity; but, second, he showed why it is not obvious what can or will count as an "entity" to be designated. Particularly in the realm of concepts and functions, both "sense" (Sinn) and "meaning" (Bedeutung) are intimately bound up with 624 modes of representation and expression-which, in a philosophical orientation (such as Husserl's) that assumes one can eliminate mediation to arrive at some originary intuition, can scarcely be acknowledged at all. Frege's essay "On Sense and Meaning" (1892) is doubly important as it illuminates a fundamental problem while illustrating an analytical method that, as developed by such philosophers and logicians as Bertrand Russell, Ludwig Wittgenstein, W. V. Quine, Alonzo Church, and others, has been rich and fruitful. While the essay is written with a logical problem in mind (that is, the relation of "equality"), it is one of the earliest examples of philosophical analysis to show that the problem pervades natural language and is not restricted to mathematics or formal logic alone. From this point of view, Frege, like C. S. Peirce, anticipates the concern of later philosophers and critics with problems of language and meaning, particularly where semantic and epistemological issues overlap but require differentiation. An earlier translation of the essay here was titled "Sense and Reference," rendering Bedeutung as "reference." But for Frege, the issue is not "reference" as such, or "representation," but the logical condition under which a statement of equality could be asserted. In the relation "a = b," "a" and "b" are presumed to be the names of relata which can be equated because they are names for the same "object." In cases such as that of the planet Venus, where a single object is being called both "morning star" and "evening star," the expressions would have a different sense but the same meaning by virtue of singling out only one object. While such "objects" of expressions need not be physical bodies but could include numbers and the truth values of propositions, the distinction is, as Frege notes, problematic in the case of a work of art, which has, in his use of the terms, Sinn or sense but not Bedeutung. While one could say that "morning star" and "evening star" both mean "the planet Venus," or "a" and "b" both mean the number 1, one would not say that Richard Burton and Hamlet both mean the same thing, since there is no commonly agreed upon way to single out what that "thing" might be. Frege was obviously intrigued by the peculiarity of the case, suggesting only that expressions with sense but not meaning (Sinn but not Bedeutung) are "representations" (see note 8); but some philosophers and logicians influenced by Frege evidently found such cases merely otiose-as when, for example, Rudolph Carnap employed Frege's distinction to declare that expressions with Sinn but not Bedeutung, like works of metaphysics and poems, were "meaningless" and without cognitive value. While part of the problem in this case is that the characteristic use of the word "meaning" in English more nearly approximates Frege's notion of Sinn, there is then no word that is not misleading to translate his notion of Bedeutung. It remains that the relation between "reference" and "representation" still resists convincing analysis, by either logical empiricism, following Frege, or phenomenology, following Husserl, since it poses a problem for metaphysics that is categorically peculiar whenever there is a representation without a referent. If one equates these terms ("reference" and "representation"), then either term has sense or meaning only in relation to objects, either empirical or transcendental. Whether one opts to destroy metaphysics or merely deconstruct it, the first alter- 625 native deprives it of meaning (in Frege's sense), while the second deprives it of both sense and meaning, but neither does away with the problem. Several major works by Frege have been translated into English: The Foundations of Arithmetic, trans. J. L. Austin (1953); The Basic Laws of Arithmetic, trans. M. Furth (1964); and Translations from the Philosophical Writings of Gottlob Frege, ed. P. Geach and M. Black (1960). Translations of several other essays are included in E. D. Klemke's important collection of critical and interpretive articles, Essays on Frege (1968). For an important essay on related issues, see Saul Kripke, "Naming and Necessity," in Semantics of Natural Language, ed. Gilbert Harman and Donald Davidson (1972). ON SENSE AND MEANING* *ON SENSE AND MEANING was first published in Zeitschrift fur Philosophie und philosophische Kritik 100 (i (1892): 25-50. This translation by Max Black is reprinted from Translations from the Philosophical Writings of Gottlob Frege, ed. Peter Geach and Max Black, 3d ed. (1980), by permission of the publisher, Basil Blackwell. Equality1 gives rise to challenging questions which are not altogether easy to answer. Is it a relation? A relation between objects, or between names or signs of objects? In my Begriffsschrif2~ I assumed the latter. The reasons which seem to favour this are the following: a=a and a=b are obviously statements of differing cognitive value; a=a holds a priori and, according to Kant, is to be labelled analytic, while statements of the form a=b often contain very valuable extensions of our knowledge and cannot always be established a priori. The discovery that the rising sun is not new every morning, but always the same, was one of the most fertile astronomical discoveries. Even to-day the reidentification of a small planet or a comet is not always a matter of course. Now if we were to regard equality as a relation between that which the names a' and b' designate, it would seem that a=b could not differ from a=a (i.e., provided a= b is true). A relation would thereby be expressed of a thing to itself, and indeed one in which each thing stands to itself but to no other thing. What we apparently want to state by a=b is that the signs or names 'a' and 'b' designate the same thing, so that those signs themselves would be under discussion; a relation between them would be asserted. But this relation would hold between the names or signs only in so far as they named or designated something. It would be mediated by the connexion of each of the two signs with the same designated thing. But this is arbitrary. Nobody can be forbidden to use any arbitrarily producible event or object as a sign for something. In that case the sentence a= b would no longer refer to the subject matter but only to its mode of designation; we would express no proper knowledge by its means. But in many cases this is just what we want to do. If the sign 'a' is distinguished from the sign 'b' only as an object (here, by means of its shape), not as a sign (i.e. not by the manner in which it designates something), the cognitive value of a = a becomes essentially equal to that of a= b, provided a b is true. A difference can arise only if the difference between the signs corresponds to a difference in the mode of presentation of the thing designated. Let a, b, c be the lines connecting the vertices of a triangle with the midpoints of the opposite sides. The point of intersection of a and b is then the same as the point of intersection of b and c. So we have different designations for the same point, and these names ('point of intersection of a and b,' 'point of intersection of b and c') likewise indicate the mode of presentation; and hence the statement contains actual knowledge. It is natural, now, to think of there being connected with a sign (name, combination of words, written mark), besides that which the sign desig- 626 nates, which may be called the meaning of the sign, also what I should like to call the sense of the sign, wherein the mode of presentation is contained. In our example, accordingly, the meaning of the expressions 'the point of intersection of a and b' and 'the point of intersection of b and c' would be the same, but not their sense. The meaning of 'evening stars would be the same as that of 'morning star,' but not the sense. It is clear from the context that by sign and name I have here understood any designation figuring as a proper name, which thus has as its meaning a definite object (this word taken in the widest range), but not a concept or a relation, which shall be discussed further in another article.3 The designation of a single object can also consist of several words or other signs. For brevity, let every such designation be called a proper name. The sense of a proper name is grasped by everybody who is sufficiently familiar with the language or totality of designations to which it belongs;4 but this serves to illuminate only a single aspect of the thing meant, supposing it to have one. Comprehensive knowledge of the thing meant would require us to be able to say immediately whether any given sense attaches to it. To such knowledge we never attain. The regular connexion between a sign, its sense, and what it means is of such a kind that to the sign there corresponds a definite sense and to that in turn a definite thing meant, while to a given thing meant (an object) there does not belong only a single sign. The same sense has different expressions in different languages or even in the same language. To be sure, exceptions to this regular behaviour occur. To every expression belonging to a complete totality of signs, there should certainly correspond a definite sense; but natural languages often do not satisfy this condition, and one must be content if the same word has the same sense in the same context. It may perhaps be granted that every grammatically well-formed expression figuring as a proper name always has a sense. But this is not to say that to the sense there also corresponds a thing meant. The words 'the celestial body most distant from the Earth' have a sense, but it is very doubtful if there is also a thing they mean. The expression 'the least rapidly convergent series' has a sense but demonstrably there is nothing it means, since for every given convergent series, another convergent, but less rapidly convergent, series can be found. In grasping a sense, one is not certainly assured of meaning anything. If words are used in the ordinary way, what one intends to speak of is what they mean. It can also happen, however, that one wishes to talk about the words themselves or their sense. This happens, for instance, when the words of another are quoted. One's own words then first designate words of the other speaker, and only the latter have their usual meaning. We then have signs of signs. In writing, the words are in this case enclosed in quotation marks. Accordingly, a word standing between quotation marks must not be taken as having its ordinary meaning. In order to speak of the sense of an expression 'A' one may simply use the phrase 'the sense of the expression "A"'. In indirect speech one talks about the sense, e.g., of another person's remarks. It is quite clear that in this way of speaking words do not have their customary meaning but designate what is usually their sense. In order to have a short expression, we will say: In indirect speech, words are used indirectly or have their indirect meaning. We distinguish accordingly the customary from the indirect meaning of a word; and its customary sense from its indirect sense. The indirect meaning of a word is accordingly its customary sense. Such exceptions must always be borne in mind if the mode of connexion between sign, sense, and meaning in particular cases is to be correctly understood. The meaning and sense of a sign are to be distinguished from the associated idea. If what a sign means is an object perceivable by the senses, my idea of it is an internal image,5 arising from memo- 627 ries of sense impressions which I have had and acts, both internal and external, which I have performed. Such an idea is often imbued with feeling; the clarity of its separate parts varies and oscillates. The same sense is not always connected, even in the same man, with the same idea. The idea is subjective: one man's idea is not that of another. There result, as a matter of course, a variety of differences in the ideas associated with the same sense. A painter, a horseman, and a zoologist will probably connect different ideas with the name 'Bucephalus.' This constitutes an essential distinction between the idea and sign's sense, which may be the common property of many people, and so is not a part of a mode of the individual mind. For one can hardly deny that mankind has a common store of thoughts which is transmitted from one generation to another.6 In the light of this, one need have no scruples in speaking simply of the sense, whereas in the case of an idea one must, strictly speaking, add whom it belongs to and at what time. It might perhaps be said: Just as one man connects this idea, and another that idea, with the same word, so also one man can associate this sense and another that sense. But there still remains a difference in the mode of connexion. They are not prevented from grasping the same sense; but they cannot have the same idea. Si duo idem faciunt, non est idem. If two persons picture the same thing, each still has his own idea. It is indeed sometimes possible to establish differences in the ideas, or even in the sensations, of different men; but an exact comparison is not possible, because we cannot have both ideas together in the same consciousness. The meaning of a proper name is the object itself which we designate by using it; the idea which we have in that case is wholly subjective; in between lies the sense, which is indeed no longer subjective like the idea, but is yet not the object itself. The following analogy will perhaps clarify these relationships. Somebody observes the Moon through a telescope. I compare the Moon itself to the meaning; it is the object of the observation, mediated by the real image projected by the object glass in the interior of the telescope, and by the retinal image of the observer. The former I compare to the sense, the latter is like the idea or experience. The optical image in the telescope is indeed one-sided and dependent upon the standpoint of observation; but it is still objective, inasmuch as it can be used by several observers. At any rate it could be arranged for several to use it simultaneously. But each one would have his own retinal image. On account of the diverse shapes of the observers' eyes, even a geometrical congruence could hardly be achieved, and an actual coincidence would be out of the question. This analogy might be developed still further, by assuming A's retinal image made visible to B; or A might also see his own retinal image in a mirror. In this way we might perhaps show how an idea can itself be taken as an object, but as such is not for the observer what it directly is for the person having the idea. But to pursue this would take us too far afield. We can now recognize three levels of difference between words, expressions, or whole sentences. The difference may concern at most the ideas, or the sense but not the meaning, or, finally, the meaning as well. With respect to the first level, it is to be noted that, on account of the uncertain connexion of ideas with words, a difference may hold for one person, which another does not find. The difference between a translation and the original text should properly not overstep the first level. To the possible difference here belong also the colouring and shading which poetic eloquence seeks to give to the sense. Such colouring and shading are not objective, and must be evoked by each hearer or reader according to the hints of the poet or the speaker. Without some affinity in human ideas art would certainly be impossible; but it can never be exactly determined how far the intentions of the poet are realized. In what follows there will be no further discussion of ideas and experiences; they have been mentioned here only to ensure that the idea aroused in the hearer by a word shall not be confused with its sense or its meaning. To make short and exact expressions possible, let the following phraseology be established: A proper name (word, sign, sign combination, expression) expresses its sense, means or designates its meaning. By employing a sign we express its sense and designate its meaning. Idealists or sceptics will perhaps long since have 628 objected: 'You talk, without further ado, of the Moon as an object; but how do you know that the name "the Moon" has any meaning? How do you know that anything whatsoever has a meaning?' I reply that when we say 'the Moon,' we do not intend to speak of our idea of the Moon, nor are we satisfied with the sense alone, but we presuppose a meaning. To assume that in the sentence 'The Moon is smaller than the Earth' the idea of the Moon is in question, would be flatly to misunderstand the sense. If this is what the speaker wanted, he would use the phrase 'my idea of the Moon.' Now we can of course be mistaken in the presupposition, and such mistakes have indeed occurred. But the question whether the presupposition is perhaps always mistaken need not be answered here; in order to justify mention of that which a sign means it is enough, at first, to point our intention in speaking or thinking. (We must then add the reservation: provided such a meaning exists.) So far we have considered the sense and meaning only of such expressions, words, or signs as we have called proper names. We now inquire concerning the sense and meaning of an entire assertoric sentence. Such a sentence contains a thought.7 Is this thought, now, to be regarded as its sense or its meaning? Let us assume for the time being that the sentence does mean something. If we now replace one word of the sentence by another having the same meaning, but a different sense, this can have no effect upon the meaning of the sentence. Yet we can see that in such a case the thought changes; since, e.g., the thought in the sentence 'The morning star is a body illuminated by the Sun' differs from that in the sentence 'The evening star is a body illuminated by the Sun.' Anybody who did not know that the evening star is the morning star might hold the one thought to be true, the other false. The thought, accordingly, cannot be what is meant by the sentence, but must rather be considered as its sense. What is the position now with regard to the meaning? Have we a right even to inquire about it? Is it possible that a sentence as a whole has only a sense, but no meaning? At any rate, one might expect that such sentences occur, just as there are parts of sentences having sense but no meaning. And sentences which contain proper names without meaning will be of this kind. The sentence 'Odysseus was set ashore at Ithaca while sound asleep' obviously has a sense. But since it is doubtful whether the name 'Odysseus,' occurring therein, means anything, it is also doubtful whether the whole sentence does. Yet it is certain, nevertheless, that anyone who seriously took the sentence to be true or false would ascribe to the name 'Odysseus' a meaning, not merely a sense; for it is of what the name means that the predicate is affirmed or denied. Whoever does not admit the name has meaning can neither apply nor withhold the predicate. But in that case it would be superfluous to advance to what the name means; one could be satisfied with the sense, if one wanted to go no further than the thought. If it were a question only of the sense of the sentence, the thought, it would be needless to bother with what is meant by a part of the sentence; only the sense, not the meaning, of the part is relevant to the sense of the whole sentence. The thought remains the same whether 'Odysseus' means something or not. The fact that we concern ourselves at all about what is meant by a part of the sentence indicates that we generally recognize and expect a meaning for the sentence itself. The thought loses value for us as soon as we recognize that the meaning of one of its parts is missing. We are therefore justified in not being satisfied with the sense of a sentence, and in inquiring also as to its meaning. But now why do we want every proper name to have not only a sense, but also a meaning? Why is the thought not enough for us? Because, and to the extent that, we are concerned with its truth-value. This is not always the case. In hearing an epic poem, for instance, apart from the euphony of the language we are interested only in the sense of the sentences and the images and feelings thereby aroused. The question of truth would cause us to abandon aesthetic delight for an attitude of scientific investigation. Hence it is a matter of no concern to us whether the name 'Odysseus,' for instance, has meaning, so long as we accept the poem as a work of art.8 It is the striving for truth that drives us always to advance from the sense to the thing meant. 629 We have seen that the meaning of a sentence may always be sought, whenever the meaning of its components is involved; and that this is the case when and only when we are inquiring after the truth-value. We are therefore driven into accepting the truth-value of a sentence as constituting what it means. By the truth-value of a sentence I understand the circumstance that it is true or false. There are no further truth-values. For brevity I call the one the True, the other the False. Every assertoric sentence concerned with what its words mean is therefore to he regarded as a proper name, and its meaning, if it has one, is either the True or the False. These two objects are recognized, if only implicitly, by everybody who judges something to be true-and so even by a sceptic. The designation of the truth values as objects may appear to be an arbitrary fancy or perhaps a mere play upon words, from which no profound consequences could be drawn. What I am calling an object can be more exactly discussed only in connexion with concept and relation. I will reserve this for another article.9 But so much should already be clear, that in every judgment,10 no matter how trivial, the step from the level of thoughts to the level of meaning (the objective) has already been taken. One might be tempted to regard the relation of the thought to the True not as that of sense to meaning, but rather as that of subject to predicate. One can, indeed, say: 'The thought that 5 is a prime number is true.' But closer examination shows that nothing more has been said than in the simple sentence '5 a prime number.' The truth claim arises in each case from the form of the assertoric sentence, and when the latter lacks its usual force, e.g., in the mouth of an actor upon the stage, even the sentence 'The thought that 5 is a prime number is true' contains only a thought, and indeed the same thought as the simple '5 is a prime number.' It follows that the relation of the thought to the True may not be compared with that of subject to predicate. Subject and predicate (understood in the logical sense) are just elements of thought; they stand on the same level for knowledge. By combining subject and predicate, one reaches only a thought, never passes from sense to meaning, never from a thought to its truth-value. One moves at the same level but never advances from one level to the next. A truth-value cannot be a part of a thought, any more than, say, the Sun can, for it is not a sense but an object. If our supposition that the meaning of a sentence is its truth-value is correct, the latter must remain unchanged when a part of the sentence is replaced by an expression with the same meaning. And this is in fact the case. Leibniz gives the definition: 'Eadem sunt, quae sibi mutuo substitui possunt, salva veritate.' If we are dealing with sentences for which the meaning of their component parts is at all relevant, then what feature except the truth-value can be found that belongs to such sentences quite generally and remains unchanged by substitutions of the kind just mentioned? If now the truth-value of a sentence is its meaning, then on the one hand all true sentences have the same meaning and so, on the other hand, do all false sentences. From this we see that in the meaning of the sentence all that is specific is obliterated. We can never be concerned only with the meaning of a sentence; but again the mere thought alone yields no knowledge, but only the thought together with its meaning, i.e. its truth-value. Judgments can be regarded as advances from a thought to a truth-value. Naturally this cannot be a definition. Judgment is something quite peculiar and incomparable. One might also say that judgments are distinctions of parts within truth-values. Such distinction occurs by a return to the thought. To every sense attaching to a truth-value would correspond its own manner of analysis. However, I have here used the word 'part' in a special sense. I have in fact transferred the relation between the parts and the whole of the sentence to its meaning, by calling the meaning of a word part of the meaning of the sentence, if the word itself is a part of the sentence. This way of speaking can certainly be attacked, because the total meaning and one part of it do not suffice to determine the remainder, and because the word 'part' is already used of bodies in another sense. A special term would need to be invented. The supposition that the truth value of a sentence is what it means shall now be put to further test. We have found that the truth-value of a sentence remains unchanged when an expression is replaced by another with the same meaning: but we have not yet considered the case in which the expression to be replaced is itself a sentence. Now if our view is 630 correct, the truth-value of a sentence containing another as part must remain unchanged when the part is replaced by another sentence having the same truth-value. Exceptions are to be expected when the whole sentence or its part is direct or indirect quotation; for in such cases as we have seen, the words do not have their customary meaning. In direct quotation, a sentence designates another sentence, and in indirect speech a thought. We are thus led to consider subordinate sentences or clauses. These occur as parts of a sentence complex, which is, from the logical standpoint, likewise a sentence-a main sentence. But here we meet the question whether it is also true of the subordinate sentence that its meaning is a truth-value. Of indirect speech we already know the opposite. Grammarians view the subordinate clauses as representatives of parts of sentences and divide them accordingly into noun clauses, adjective clauses, adverbial clauses. This might generate the supposition that the meaning of a subordinate clause was not a truth-value but rather of the same kind as the meaning of a noun or adjective or adverb-in short, of a part of a sentence, whose sense was not a thought but only a part of a thought. Only a more thorough investigation can clarify the issue. In so doing, we shall not follow the grammatical categories strictly, but rather group together what is logically of the same kind. Let us first search for cases in which the sense of the subordinate clause, as we have just supposed, is not an independent thought. The case of an abstract11 noun clause, introduced by 'that,' includes the case of indirect quotation, in which we have seen the words to have their indirect meaning, coincident with what is customarily their sense. In this case, then, the subordinate clause has for its meaning a thought, not a truth-value; as sense not a thought, but the sense of the words 'the thought that (etc.),' which is only a part of the thought in the entire complex sentence. This happens after 'say,' 'hear,' 'be of the opinion,' 'be convinced,' 'conclude,' and similar words.12 There is a different, and indeed somewhat complicated, situation after words like 'perceive,' 'know,' 'fancy,' which are to be considered later. That in the cases of the first kind the meaning of the subordinate clause is in fact the thought can also be recognized by seeing that it is indifferent to the truth of the whole whether the subordinate clause is true or false. Let us compare, for instance, the two sentences 'Copernicus believed that the planetary orbits are circles' and 'Copernicus believed that the apparent motion of the sun is produced by the real motion of the Earth.' One sub-ordinate clause can be substituted for the other without harm to the truth. The main clause and the subordinate clause together have as their sense only a single thought, and the truth of the whole includes neither the truth nor the untruth of the subordinate clause. In such cases it is not permissible to replace one expression in the subordinate clause by another having the same customary meaning, but only by one having the same indirect meaning, i.e. the same customary sense. Somebody might conclude: The meaning of a sentence is not its truth-value, for in that case it could always be replaced by another sentence of the same truth-value. But this proves too much; one might just as well claim that the meaning of 'morning star' is not Venus, since one may not always say 'Venus' in place of 'morning star.' One has the right to conclude only that the meaning of a sentence is not always its truth value, and that 'morning star' does not always mean the planet Venus, viz, when the word has its indirect meaning. An exception of such a kind occurs in the subordinate clause just considered which has a thought as its meaning. If one says 'It seems that...' one means 'It seems to me that .. .' or 'I think that . . .' We therefore have the same case again. The situation is similar in the case of expressions such as 'to be pleased,' 'to regret,' 'to approve,' 'to blame,' 'to hope,' 'to fear.' If, toward the end of the battle of Waterloo,13 Wellington was glad that the Prussians were coming, the basis for his joy was a conviction. Had he been deceived, he would have been no less pleased so long as his illusion lasted; and before he became so convinced he could not have been pleased that the Prussians were coming-even though in fact they might have been already approaching. Just as a conviction or a belief is the ground of a 631 feeling, it can, as in inference, also be the ground of a conviction. In the sentence: 'Columbus inferred from the roundness of the Earth that he could reach India by travelling towards the west,' we have as the meanings of the parts two thoughts, that the Earth is round, and that Columbus by travelling to the west could reach India. All that is relevant here is that Columbus was convinced of both, and that the one conviction was a ground for the other. Whether the Earth is really round and Columbus could really reach India by travelling west, as he thought, is immaterial to the truth of our sentence; but it is not immaterial whether we replace 'the Earth' by 'the planet which is accompanied by a moon whose diameter is greater than the fourth part of its own.' Here also we have the indirect meaning of the words. Adverbial final clauses beginning 'in order that' also belong here; for obviously the purpose is a thought; therefore: indirect meaning for the words, subjunctive mood. A subordinate clause with 'that' after 'command,' 'ask,' 'forbid,' would appear in direct speech as an imperative. Such a sentence has no meaning but only a sense. A command, a request, are indeed not thoughts, but they stand on the same level as thoughts. Hence in subordinate clauses depending upon 'command,' 'ask,' etc., words have their indirect meaning. The meaning of such a clause is therefore not a truth-value but a command, a request, and so forth. The case is similar for the dependent question in phrases such as 'doubt whether' 'not to know what.' It is easy to see that here also the words are to be taken to have their indirect meaning. Dependent clauses expressing questions and beginning with 'who,' 'what,' 'where,' 'when,' 'how,' 'by what means,' etc., seem at times to approximate very closely to adverbial clauses in which words have their customary meanings. These cases are distinguished linguistically [in Germani by the mood of the verb. With the subjunctive, we have a dependent question and indirect meanings of the words, so that a proper name cannot in general be replaced by another name of the same object. In the cases so far considered the words of the subordinate clauses had their indirect meaning, and this made it clear that the meaning of the subordinate clause itself was indirect, i.e. not a truth-value but a thought, a command, a request, a question. The subordinate clause could be regarded as a noun, indeed one could say: as a proper name of that thought, that command, etc., which it represented in the context of the sentence structure. We now come to other subordinate clauses, in which the words do have their customary meaning without however a thought occurring as sense and a truth-value as meaning. How this is possible is best made clear by examples. Whoever discovered the elliptic form of the planetary orbits died in misery. If the sense of the subordinate clause were here a thought, it would have to be possible to express it also in a separate sentence. But it does not work, because the grammatical subject 'whoever' has no independent sense and only mediates the relation with the consequent clause 'died in misery.' For this reason the sense of the subordinate clause is not a complete thought, and what it means is Kepler, not a truth value. One might object that the sense of the whole does contain a thought as part, viz, that there was somebody who first discovered the elliptic form of the planetary orbits; for whoever takes the whole to be true cannot deny this part. This is undoubtedly so; but only because otherwise the dependent clause 'whoever discovered the elliptic form of the planetary orbits' would have nothing to mean. If anything is asserted there is always an obvious presupposition that the simple or compound proper names used have meaning. If therefore one asserts 'Kepler died in misery,' there is a presupposition that the name 'Kepler' designates something; but it does not follow that the sense of the sentence 'Kepler died in misery' contains the thought that the name 'Kepler' designates something. If this were the case the negation would have to run not Kepler did not die in misery but Kepler did not die in misery, or the name 'Kepler' has no reference. That the name 'Kepler' designates something is just as much a presupposition for the assertion Kepler died in misery as for the contrary assertion. Now languages have the fault of containing expressions which fail to 632 designate an object (although their grammatical form seems to qualify them for that purpose) because the truth of some sentence is a prerequisite. Thus it depends on the truth of the sentence: There was someone who discovered the elliptic form of the planetary orbits whether the subordinate clause Whoever discovered the elliptic form of the planetary orbits really designates an object, or only seems to do so while in fact there is nothing for it to mean. And thus it may appear as if our subordinate clause contained as a part of its sense the thought that there was somebody who discovered the elliptic form of the planetary orbits. If this were right the negation would run: Either whoever discovered the elliptic form of the planetary orbits did not die in misery or there was nobody who discovered the elliptic form of the planetary orbits. This arises from an imperfection of language, from which even the symbolic language of mathematical analysis is not altogether free; even there combinations of symbols can occur that seem to mean something but (at least so far) do not mean anything, e.g. divergent infinite series. This can be avoided, e.g., by means of the special stipulation that divergent infinite series shall mean the number 0. A logically perfect language (Begriffsschrift) should satisfy the conditions, that every expression grammatically well constructed as a proper name out of signs already introduced shall in fact designate an object, and that no new sign shall be introduced as a proper name without being secured a meaning. The logic books contain warnings against logical mistakes arising from the ambiguity of expressions. I regard as no less pertinent a warning against apparent proper names without any meaning. The history of mathematics supplies errors which have arisen in this way. This lends itself to demagogic abuse as easily as. ambiguity-perhaps more easily. 'The will of the people' can serve as an example; for it is easy to establish that there is at any rate no generally accepted meaning for this expression. It is therefore by no means unimportant to eliminate the source of these mistakes, at least in science, once and for all. Then such objections as the one discussed above would become impossible, because it could never depend upon the truth of a thought whether a proper name had meaning. With the consideration of these noun clauses may be coupled that of types of adjective and adverbial clauses which are logically in close relation to them. Adjective clauses also serve to construct compound proper names, though, unlike noun clauses, they are not sufficient by themselves for this purpose. These adjective clauses are to be regarded as equivalent to adjectives. Instead of 'the square root of 4 which is smaller than 0,' one can also say 'the negative square root of 4.' We have here the case of a compound proper name constructed from the expression for a concept with the help of the singular definite article. This is at any rate permissible if the concept applies to one and only one single object.'14 Expressions for concepts can be so constructed that marks of a concept are given by adjective clauses as, in our example, by the clause 'which is smaller than 0.' It is evident that such an adjective clause cannot have a thought as sense or a truth-value as meaning, any more than the noun clause could. Its sense, which can also in many cases be expressed by a single adjective, is only a part of a thought. Here, as in the case of the noun clause, there is no independent subject and therefore no possibility of reproducing the sense of the subordinate clause in an independent sentence. Places, instants, stretches of time, logically considered, are objects; hence the linguistic designation of a definite place, a definite instant, or a stretch of time is to be regarded as a proper name. Now adverbial clauses of place and time can be used to construct such a proper name in much the same way as we have seen noun and adjective clauses can. In the same way, expressions for concepts that apply to places, etc., can be constructed. It is to be noted here also that the sense of these subordinate clauses cannot be reproduced in an independent sentence, since an essential component, viz, the determina- 633 tion of place or time, is missing and is just indicated by a relative pronoun or a conjunction.15 In conditional clauses, also, there most often recognizably occurs an indefinite indicator, with a correlative indicator in the dependent clause. (We have already seen this occur in noun, adjective, and adverbial clauses.) In so far as each indicator relates to the other, both clauses together form a connected whole, which as a rule expresses only a single thought. In the sentence If a number is less than r and greater than 0, its square is less than and greater than 0 the component in question is 'a number' in the antecedent clause and 'its' in the consequent clause. It is by means of this very indefiniteness that the sense acquires the generality expected of a law. It is this which is responsible for the fact that the antecedent clause alone has no complete thought as its sense and in combination with the consequent clause expresses one and only one thought, whose parts are no longer thoughts. It is, in general, incorrect to say that in the hypothetical judgment two judgments are put in reciprocal relationship. If this or something similar is said, the word 'judgment' is used in the same sense as I have connected with the word 'thought,' so that I would use the formulation: 'A hypothetical thought establishes a reciprocal relationship between two thoughts.' This could be true only if an indefinite indicator is absent;16 but in such a case there would also be no generality. If an instant of time is to be indefinitely indicated in both the antecedent and the consequent clause, this is often achieved merely by using the present tense of the verb, which in such a case however does not indicate the temporal present. This grammatical form is then the indefinite indicator in the main and subordinate clauses. An example of this is: 'When the Sun is in the tropic of Cancer, the longest day in the northern hemisphere occurs.' Here, also, it is impossible to express the sense of the subordinate clause in a full sentence, because this sense is not a complete thought. If we say: 'The Sun is in the tropic of Cancer,' this would refer to our present time and thereby change the sense. Neither is the sense of the main clause a thought; only the whole, composed of main and subordinate clauses, has such a sense. It may be added that several common components may be indefinitely indicated in the antecedent and consequent clauses. It is clear that noun clauses with 'who' or 'what' and adverbial clauses with 'where,' 'when,' 'wherever,' 'whenever' are often to be interpreted as having the sense of antecedent clauses, e.g. 'who touches pitch, defiles himself.' Adjective clauses can also take the place of conditional clauses. Thus the sense of the sentence previously used can be given in the form 'The square of a number which is less than 1 and greater than 0 is less than and greater than 0. The situation is quite different if the common component of the two clauses is designated by a proper name. In the sentence: Napoleon, who recognized the danger to his right flank, himself led his guards against the enemy position two thoughts are expressed: 1. Napoleon recognized the danger to his right flank 2. Napoleon himself led his guards against the enemy position. 634 When and where this happened is to be fixed only by the context, but is nevertheless to be taken as definitely determined thereby. If the entire sentence is uttered as an assertion, we thereby simultaneously assert both component sentences. If one of the parts is false, the whole is false. Here we have the case that the subordinate clause by itself has a complete thought as sense (if we complete it by indication of place and time). The meaning of the subordinate clause is accordingly a truth-value. We can therefore expect that it may be replaced, without harm to the truth-value of the whole, by a sentence having the same truth-value. This is indeed the case; but it is to be noticed that for purely grammatical reasons, its subject must be 'Napoleon,' for only then can it be brought into the form of an adjective clause attaching to 'Napoleon.' But if the demand that it be expressed in this form is waived, and the connexion shown by 'and,' this restriction disappears. Subsidiary clauses beginning with 'although' also express complete thoughts. This conjunction actually has no sense and does not change the sense of the clause but only illuminates it in a peculiar fashion.17 We could indeed replace the concessive clause without harm to the truth of the whole by another of the same truth-value; but the light in which the clause is placed by the conjunction might then easily appear unsuitable, as if a song with a sad subject were to be sung in a lively fashion. In the last cases the truth of the whole included the truth of the component clauses. The case is different if an antecedent clause expresses a complete thought by containing, in place of an indefinite indicator, a proper name or something which is to be regarded as equivalent. In the sentence If the Sun has already risen, the sky is very cloudy the time is the present, that is to say, definite. And the place is also to be thought of as definite. Here it can be said that a relation between the truth-values of antecedent and consequent clauses has been asserted, viz, that the case does not occur in which the antecedent means the True and the consequent the False. Accordingly, our sentence is true if the Sun has not yet risen, whether the sky is very cloudy or not, and also if the Sun has risen and the sky is very cloudy. Since only truth-values are here in question, each component clause can be replaced by another of the same truth-value without changing the truth-value of the whole. To be sure, the light in which the subject then appears would usually be unsuitable; the thought might easily seem distorted; but this has nothing to do with its truth-value. One must always observe that there are overtones of subsidiary thoughts, which are however not explicitly expressed and therefore should not be reckoned in the sense. Hence, also, no account need be taken of their truth-values.18 The simple cases have now been discussed. Let us review what we have learned. The subordinate clause usually has for its sense not a thought, but only a part of one, and consequently no truth-value is being meant. The reason for this is either that the words in the subordinate clause have indirect meaning, so that the meaning, not the sense, of the subordinate clause is a thought; or else that, on account of the presence of an indefinite indicator, the subordinate clause is incomplete and expresses a thought only when combined with the main clause. It may happen, however, that the sense of the subsidiary clause is a complete thought, in which case it can be replaced by another of the same truth-value without harm to the truth of the whole-provided there are no grammatical obstacles. An examination of 'all the subordinate clauses which one may encounter will soon provide some which do not fit well into these categories. The reason, so far as I can see, is that these subordinate clauses have no such simple sense. Almost always, it seems, we connect with the main thoughts expressed by us subsidiary thoughts which, although not expressed, are associated with our words, in accordance with psychological laws, by the hearer. And since the subsidiary thought appears to be connected with our words on its own account, almost like the main thought itself, we want it also to be expressed. The sense of the sentence is thereby enriched, and it may well happen that we have more simple thoughts than clauses. In many cases the 635 sentence must be understood in this way, in others it may be doubtful whether the subsidiary thought belongs to the sense of the sentence or only accompanies it.19 One might perhaps find that the sentence Napoleon, who recognized the danger to his right flank, himself led his guards against the enemy position expresses not only the two thoughts shown above, but also the thought that the knowledge of the danger was the reason why he led the guards against the enemy position. One may in fact doubt whether this thought is just slightly suggested or really expressed. Let the question be considered whether our sentence is false if Napoleon's decision had already been made before he recognized the danger. If our sentence could be true in spite of this, the subsidiary thought should not be understood as part of the sense. One would probably decide in favour of this. The alternative would make for a quite complicated situation: We would have more simple thoughts than clauses. If the sentence Napoleon recognized the danger to his right flank were now to be replaced by another having the same truth value, e.g. Napoleon was already more than 45 years old not only would our first thought be changed, but also our third one. Hence the truth-value of the latter might change-viz, if his age was not the reason for the decision to lead the guards against the enemy. This shows why clauses of equal truth-value cannot always be substituted for one another in such cases. The clause expresses more through its connexion with another than it does in isolation. Let us now consider cases where this regularly happens. In the sentence: Bebel fancies that the return of Alsace-Lorraine would appease France's desire for revenge 635 two thoughts are expressed, which are not however shown by means of antecedent and consequent clauses, viz.: (1) Bebel believes that the return of AlsaceLorraine would appease France's desire for revenge (2) the return of Alsace-Lorraine would not appease France's desire for revenge. In the expression of the first thought, the words of the subordinate clause have their indirect meaning, while the same words have their customary meaning in the expression of the second thought. This shows that the subordinate clause in our original complex sentence is to be taken twice over, with different meanings: once for a thought, once for a truth value. Since the truth-value is not the total meaning of the subordinate clause, we cannot simply replace the latter by another of equal truth-value. Similar considerations apply to expressions such as 'know,' 'discover,' 'it is known that.' By means of a subordinate causal clause and the associated main clause we express several thoughts, which however do not correspond separately to the original clauses. In the sentence: 'Because ice is less dense than water, it floats on water' we have (1) Ice is less dense than water; (2) If anything is less dense than water, it floats on water; (3) Ice floats on water. The third thought, however, need not be explicitly introduced, since it is contained in the remaining two. On the other hand, neither the first and third nor the second and third combined would furnish the sense of our sentence. It can now be seen that our subordinate clause because ice is less dense than water expresses our first thought, as well as a part of our second. This is how it comes to pass that our subsidiary clause cannot be simply replaced by another of equal truth value; for this would alter our second thought and thereby might well alter its truth value. The situation is similar in the sentence 636 If iron were less dense than water, it would float on water. Here we have the two thoughts that iron is not less dense than water, and that something floats on water if it is less dense than water. The subsidiary clause again expresses one thought and a part of the other. If we interpret the sentence already considered After Schleswig-Holstein was separated from Denmark, Prussia and Austria quarrelled in such a way that it expresses the thought that Schleswig-Holstein was once separated from Denmark, we have first this thought, and secondly the thought that, at a time more closely determined by the subordinate clause, Prussia and Austria quarrelled. Here also the subordinate clause expresses not only one thought but also a part of another. Therefore it may not in general be replaced by another of the same truth-value. It is hard to exhaust all the possibilities given by language; but I hope to have brought to light at least the essential reasons why a subordinate clause may not always be replaced by another of equal truth value without harm to the truth of the whole sentence structure. These reasons arise: (1) when the subordinate clause does not have a truth-value as its meaning, inasmuch as it expresses only a part of a thought; (2) when the subordinate clause does have a truth-value as its meaning but is not restricted to so doing, inasmuch as its sense includes one thought and part of another. The first case arises: (a) for words having indirect meaning (b) if a part of the sentence is only an indefinite indicator instead of a proper name. In the second case, the subsidiary clause may have to be taken twice over, viz, once in its customary meaning, and the other time in indirect meaning; or the sense of a part of the subordinate clause may likewise be a component of another thought, which, taken together with the thought directly expressed by the subordinate clause, makes up the sense of the whole sentence. It follows with sufficient probability from the foregoing that the cases where a subordinate clause is not replaceable by another of the same value cannot be brought in disproof of our view that a truth-value is the meaning of a sentence that has a thought as its sense. Let us return to our starting point. When we found 'a=a' and 'a=b' to have different cognitive values, the explanation is that for the purpose of knowledge, the sense of the sentence, viz., the thought expressed by it, is no less relevant than its meaning, i.e. its truth-value. If now a=b, then indeed what is meant by 'b' is the same as what is meant by 'a,' and hence the truth-value of 'a=b' is the same as that of 'a= a.' In spite of this, the sense of 'b' may differ from that of 'a,' and thereby the thought expressed in 'a= b' differs from that of a=a.' In that case the two sentences do not have the same cognitive value. If we understand by 'judgment' the advance from the thought to its truth-value, as in the present paper, we can also say that the judgments are different. 1 'I use this word in the sense of identity and understand 'a=b' to have the sense of 'a is the same as b' or a and b coincide.' [Au.I 2 The reference is to Frege's Begriffsschrift, eine der arithmet:schen nachgebildete Formelsprache des reinen Denkens (HalIe, (1879). [Tr.] 3 See his 'Ueber Begriff und Gegenstand' (Viertel,ahrsschr:ft fur wissenschaftliche Philosophie XVI (1892.1, 192.- 2.05); in Translations, pp. 42.-55. lTr.l 4 4In the case of an actual proper name such as 'Aristotle' opinions as to the sense may differ. It might, for instance, be taken to be the following: the pupil of Plato and teacher of Alexander the Great. Anybody who does this will attach another sense to the sentence 'Aristotle was born in Stagira' than will a man who takes as the sense of the name: the teacher of Alexander the Great who was born in Stagira. So long as the thing meant remains the same, such variations of sense may be tolerated, although they are to be avoided in the theoretical structure of a demonstrative science and ought not to occur in a perfect language. [Au.] 5 We may include with ideas direct experiences: here, sense-impressions and acts themselves take the place of the traces which they have left in the mind. The distinction is unimportant for our purpose, especially since memories of sense-impressions and acts always go along with such impressions and acts themselves to complete the perpetual image. One may on the other hand understand direct experience as including any object in so far as it is sensibly perceptible or spatial. lAu.l 6 Hence it is inadvisable to use the word 'idea' to designate something so basically different. [Au] 7 By a thought I understand not the subjective performance of thinking but its objective content, which is capable of being the common property of several thinkers. IAu.l 8 It would be desirable to have a special term for signs having only sense. If we name them, say, representations, the words of the actors on the stage would be representations; indeed the actor himself would be a representation. [Au.] 9 See his 'Ueber Begriff und Gegenstand' (1892.), in Translations, pp. 42.-45. lTr.l See note 3 above. [Eds.) 10 A judgment, for me, is not the mere grasping of a thought, but the admission of its truth. [Au.] 11 Frege probably means clauses grammatically replaceable by an abstract noun-phrase; e.g., 'Smith denies that dragons exist' = 'Smith denies the existence of dragons'; or again, in this context after 'denies', 'that Brown is wise' is replaceable by 'the wisdom of Brown.' [Tr.] 12 In'A lied in saying he had seen B,' the subordinate clause designates a thought which is said (1) to have been asserted by A (2) while A was convinced of its falsity. [Au.] 13 Frege uses the Prussian name for the battle-'Belle Alliance.' [Tr.] 14 In accordance with what was said before, an expression of the kind in question must actually always be assured of meaning, by means of a special stipulation, e.g. by the convention that it shall count as meaning 0 when the concept applies to no object or to more than one. pAu.] 15 In the case of these sentences, various interpretations are easily possible. The sense of the sentence, 'After Schleswig-Holstein was separated from Denmark, Prussia and Austria quarrelled' can be rendered in the form 'After the separation of Schleswig-Holstein from Denmark, Prussia and Austria quarrelled.' In this version, it is surely sufficiently clear that the sense is not to be taken as having as a part the thought that Schleswig-Holstein was once separated from Denmark, but that this is the necessary presupposition in order for the expression 'after the separation of Schleswig-Holstein from Denmark' to have any meaning at all. To be sure, our sentence can also be interpreted as saying that Schleswig-Holstein was once separated from Denmark. We then have a case which is to be considered later. In order to understand the difference more clearly, let us project ourselves into the mind of a Chinese who, having little knowledge of European history, believes it to be false that Schleswig-Holstein was ever separated from Denmark. He will take our sentence, in the first version, to be neither true nor false but will deny it to have any meaning, on the ground that its subordinate clause lacks a meaning. This clause would only apparently determine a time. If he interpreted our sentence in the second way, however, he would find a thought expressed in it which he would take to be false, beside a part which would be without meaning for him. [Au.l 16 At times there is no linguistically explicit indicator and one must be read off from the entire context. [Au.] 17 Similarly in the case of 'but,' 'yet.' [Au.] 18 The thought of our sentence might also be expressed thus: 'Either the Sun has not risen yet or the sky is very cloudy'-which shows how this kind of sentence connexion is to be understood. [Au.] 19 This may be important for the question whether an assertion is a lie, or an oath a perjury. [Au.]