Moritz Schlick

“ Why should we suppose that there would be any difference if all living beings on our planet, or indeed everywhere in the universe, were extinguished? There can be no doubt that on the strength of empirical evidence the existence of living beings is no necessary condition for the existence of the rest of the world.
The question 'Will the world go on existing after I am dead?' has no meaning unless it is interpreted as asking 'Does the existence of the stars etc.
depend upon the life or death of a human being?', and this question is answered in the negative by experience. ”

“ It is logically legitimate and actually the normal way in ordinary life and even in science to answer a question concerning the meaning of a proposition by simply repeating it either more distinctly or in slightly different words. Under what circumstances, then, can there be any sense in asking for the meaning of a statement which is well before our eyes or ears? ”

“ The possibility of verification does not rest on any ‘experiential thruth’, on a law of nature or any other true general proposition, but is determined solely by our definitions, by the rules which have been fixed for our language, or which we can fix arbitrarily at any moment. All of these rules ultimately point to ostensive definitions, as we have explained, and through them verifiability is linked to experience in the first sense of the word. ”

“ The mere statement that no sentence has meaning unless we are able to indicate a way of testing its truth or falsity is not very useful if we do not explain very carefully the signification of the phrases ‘method of testing’ and ‘verifiability’. ”

“ An opponent of our view might find a dangerous paradox or even a contradiction in the preceding explanations, because on the one hand we insisted so strongly on what has been called the “empirical-meaning requirement”, and on the other hand we assert most emphatically that meaning and verifiability do not depend on any empirical conditions whatever, but are determined by purely logical possibilities. The opponent will object: if meaning is a matter of experience, how can it be a matter of definition and logic? ”

“ The idealist or solipsist who says, T can feel only my own pain', or, more generally, T can be aware only of the data of my own consciousness', believes that he is uttering a necessary, self-evident truth which no possible experience can force him to sacrifice. He will have to admit the possibility of circumstances such as those we described for our fictitious world; but, he will say, even if I feel pain every time when another body O is hurt, I shall never say, 'I feel O's pain', but always, 'My pain is in O's body'. ”

“ But if we should say in general that verifiability of an assertion implies possibility of ‘imagining’ the asserted fact, this would be true only in a restricted sense. It would not be true in so far as the possibility is of the empirical kind, i.e., implying specific human capacities. I do not think, for instance, that we can be accused of talking nonsense if we speak of a universe of ten dimensions, or of beings possessing sense-organs and having perceptions entirely different from ours ”

“ And the empirical circumstances are such that we have every reason to believe the hypothesis to be true. We are as sure of it as of the best founded physical laws that science has discovered.
As a matter of fact, we have already pointed out that there are certain regularities in the world which experience shows to be entirely independent of what happens to human beings on the earth. ”

“ The sentence 'All experience is first-person experience' will either mean the simple empirical fact that all data are in certain respects dependent on the state of the nervous system of my body M, or it will be meaningless. Before this physiological fact is discovered, experience is not 'my' experience at all, it is self-sufficient and does not 'belong' to anybody. The proposition 'The ego is the centre of the world' may be regarded as an expression of the same fact- and has meaning only if it refers to the body. ”

“ If it should be urged that the souls of the deceased might inhabit some super celestial space where they would not be accessible to our perception, and that therefore the truth or falsity of the assertion could never be tested, the reply would be that if the words 'supercelestial space' are to have any meaning at all, that space must be defined in such a way that the impossibility of reaching it or of perceiving anything in it would be merely empirical, so that some means of overcoming the difficulties could at least be described, although it might be beyond human power to put them into use. ”

“ The hypothesis of immortality is an empirical statement which owes its meaning to its verifi ability, and it has no meaning beyond the possibility of verification. If it must be admitted that science could make no experiment the negative result of which would disprove it, this is true only in the same sense in which it is true for many •other hypotheses of similar structure — especially those that have sprung up from other motives than the knowledge of a great many facts of experience which must be regarded as giving a high probability to the hypothesis. ”

“ The empirical circumstances are all-important when you want to know if a proposition is true (which is the concern of the scientist) , but they can have no influence on the meaning of the proposition (which is the concern of the philosopher) . Professor Lewis has seen and expressed this very clearly (loc. cit. 142, first six lines) , and our Vienna positivism, as far as I can answer for it, is in complete agreement with him on this point. It must be emphasized that when we speak of verifiability we mean logical possibility of verification, and nothing but this. ”

“ We know from our considerations in section I that a proposition cannot be given ‘ready made’; that meaning does not inhere in a sentence where it might be discovered, but that it must be bestowed upon it. And this is done by applying to the sentence the rules of the logical grammar of our language, as explained in section I. These rules are not facts of nature which could be ‘discovered’, but they are prescriptions stipulated by acts of definition. And these definitions have to be known to those who pronounce the sentence in question and to those who hear or read it. ”

“ Thus logical possibility or impossibility of verification is always selfimposed. If we utter a sentence without meaning it is always our own fault.
The tremendous philosophic importance of this last remark will be realized when we consider that what we said about the meaning of assertions applies also to the meaning of questions. There are, of course, many questions which can never be answered by human beings. ”

“ If it is merely empirical in the sense defined, if it is due to the chance circumstances to which our human existence is confined, there may be reason to lament our fate and the weakness of our physical and mental powers, but the problem could never be said to be absolutely insoluble, and there would always be some hope, at least for future generations. ”

“ The unique position of the 'self is not a basic property of all experience, but is itself a fact (among other facts) of experience. Idealism (as represented by Berkeley's "esse = percipi" or by Schopenhauer's "Die Welt ist meine Vorstellung") and other doctrines with egocentric tendencies commit the great error of mistaking the unique position of the ego, which is an empirical fact, for a logical, a priori truth, or, rather, substituting the one for the other. It is worth while to investigate this matter and analyse the sentence which seems to express the egocentric predicament. ”

“ Empirical possibility is determined by the laws of nature, but meaning and verifiability are entirely independent of them. Everything that I can describe or define is logically possible — and definitions are in no way bound up with natural laws. The proposition ‘Rivers flow uphill’ is meaningful, but happens to be false because the fact it describes is physically impossible. It will not deprive a proposition of its meaning if the conditions which I stipulate for its verification are incompatible with the laws of nature ”

“ We do not find this concept in the language of unsophisticated, primitive people; they do not say, T perceive a tree', but simply, 'there is a tree'. 'Perception' implies the distinction between a subject which perceives and an object which is perceived. Originally the perceiver is the sense-organ or the body to which it belongs, but since the body itself — including the nervous system — is also one of the perceived things, the original view is soon 'corrected' by substituting for the perceiver a new subject, which is called 'ego' or 'mind' or 'consciousness'. ”

“ The meaning of a proposition is the method of its verification. ”

“ Verifiability, which is the sufficient and necessary condition of meaning, is a possibility of the logical order; it is created by constructing the sentence in accordance with the rules by which its terms are defined. The only case in which verification is (logically) impossible is the case where you have made it impossible by not setting any rules for its verification. Grammatical rules are not found anywhere in nature, but are made by man and are, in principle, arbitrary ”

“ For the empirical circumstances may alter, human facilities may develop, and even the laws of nature may change (perhaps even suddenly and in such a way that the universe would be thrown open to much more extended investigation) . A problem of this kind might be called practically unanswerable or technically unanswerable, and might cause the scientist great trouble, but the philosopher, who is concerned with general principles only, would not feel terribly excited about it. ”

“ The laws of motion of the celestial bodies are formulated entirely without reference to any human bodies, and this is the reason why we are justified in maintain thating they will go on in their courses after mankind has vanished from the earth. Experience shows no connection between the two kinds of events. We observe that the course of the stars is no more changed by the death of human beings than, say, by the eruption of a volcano, or by a change of government in China. ”

“ But this is exactly what the true solipsist refuses to do. He contends that no experience whatever could possibly contradict him, because it would always necessarily have the peculiar for-me character, which may be described by the 'egocentric predicament'. In other words, he is well aware that solipsism cannot be based on Q as long as Q is, by definition, nothing but another way of expressing P. As a matter of fact, the solipsist who makes the statement Q attaches a different meaning to the same words; he does not wish merely to assert P, but he intends to say something entirely different. ”

“ The concept of 'ego' is a construction put upon the same fact, and we could easily imagine a world in which this concept would not have been formed, where there would be no idea of an insurmountable barrier between what is inside the Me and what is outside of it. It would be a world in which occurrences like those corresponding to proposition R and similar ones were the rule, and in which the facts of 'memory' were not so pronounced as they are in our actual world. ”

“ The source of these difficulties is to be found in the fact that very often we do not know how to handle our own words; we speak or write without having first agreed upon a definite logical grammar which will constitute the signification of our terms. We commit the mistake of thinking that we know the meaning of a sentence (i.e., understand it as a proposition) if we are familiar with all the words occurring in it. ”

“ It is clear that in these cases the answer is given by experience, as the result of experiments performed in the past. Any judgment about empirical possibility is based on experience and will often be rather uncertain; there will be no sharp boundary between possibility and impossibility. ”

“ We cannot declare this statement of the idealist to be false; it is just a different way of adapting our language to the imagined new circumstances, and the rules of language are, in principle, arbitrary. But, of course, some uses of our words may recommend themselves as practical and well adapted; others may be condemned as misleading. Let us examine the idealist's attitude from this point of view. ”

“ Geometry itself is the grammar of our propositions about ‘spatial’ relations, and it is not very difficult to see how assertions about physical properties and spatial relations are connected with ‘sense-data’ by ostensive definitions. ”

“ It is rather unfortunate that Carnap has advocated what he calls "methodological solipsism", and that in his construction of all concepts out of elementary data the "eigenpsychische Gegenstande" (for-me entities) come first and form the basis fro the construction of physical objects, which finally lead to the concept of other selves; but if there is any mistake here it is chiefly in the terminology, not in the thought. "Methodological solipsism" is not a kind of solipsism, but a method of building up concepts. ”

“ The height of a tower cannot be 100 feet and 150 feet at the same time; a child cannot be naked and dressed at the same time — not because we are unable to imagine it, but because our definitions of ‘height’, of the numerals, of the terms ‘naked’ and ‘dressed’, are not compatible with the particular combinations of those words in our examples. 'They are not compatible with such combinations' means that the rules of our language have not provided any use for such combinations; they do not describe any fact. ”