Moritz Schlick

“ The position of this philosophy is unassailable, because it rests on the acknowledgment of the hardest facts and the study of the strictest logic. On these foundations our Philosophy of Experience stands very securely as on a firm rock amidst a wild sea of various philosophical opinions. It is neither skeptical nor dogmatic, it cannot interfere with science or with human values; its only object is understanding. Only in this way can it attain that serene attitude which belongs to all genuine philosophy: the attitude of Wisdom. ”

“ This issue between rationalism and empiricism went on continuously through the centuries, and the chief reason why rationalism was very often deemed to be victorious lay in the fact of the existence of what is called logical and mathematical truths. All the best thinkers from Plato’s time on recognized that these truths certainly did not rest on any experience, and yet nobody could deny that they not only were really true, but even the most firmly established truths of all, and without doubt applicable to reality. ”

“ There is an enormous difference between these two kinds of impossibility. We must distinguish between those problems which are insoluble in principle, and those which man cannot solve because he does not happen to have the technical means necessary for the solution. Whenever he comes across an unanswerable question, the philosopher must ask himself to which of these two classes it belongs. It is likely that no human being will ever know what the back of the moon looks like, because the moon always turns only one and the same side towards the earth. ”

“ All propositions, all languages, all systems of symbols, also all philosophies, want to express something. They can do this only if there is something there that can be expressed: it is the material of all knowledge, and to say that it must be given by experience is but another way of saying that something must be there before we can have knowledge of it and about it. ”

“ But our new empiricism is in no way skeptical; on the contrary, it denies that there is in principle any limit to human knowledge; the existing limits are not of an essential, philosophical nature, but only accidental ones. They are only practical, technical, and may some time be overcome. According to our view all knowledge is based on experience, but this does no longer mean any restriction of knowledge. In the older views the impossibility of metaphysics was due to some regrettable imperfection or incapacity of the human mind ”

“ In Kant’s time and in the nineteenth century the tremendous difficulties involved in this problem could not be clearly seen, and the older thinkers arrived at their results in rather a superficial manner, but when during the last two or three decades the problem of the nature of mathematical propositions presented itself to the mathematicians within their own territory and called for a definite solution for the sake of pure mathematics alone, it was taken up again by logicians empirically-minded philosophers, and mathematicians, under the leadership of the most subtle and critical of the last. ”

“ We see from this explanation why the meta-physician is usually a rationalist at the same time, while the empiricist rejects the possibility of metaphysics, i. e. of any knowledge that would reach beyond the world of experience. It is true that in the history of philosophy we sometimes find intermediate points of view, so that the equations rationalist = metaphysician, empirist = non-metaphysician, are not quite correct historically, but those views are due to certain confusions which complicate the matter and with which we do not have to concern ourselves. ”

“ But, on the other hand, there is nothing ever really proved by analogy; so, if Descartes' argument leads to anything at all, it must lead to doubt concerning the existence of any consciousness of other beings, whether human or animal. And it seems that his doubt must remain forever, as it is generally admitted that it is absolutely impossible for us to become directly aware of any one else's consciousness. We cannot have any immediate knowledge of the mental states of others. ”

“ We are able to make many reliable statements about the development of planets like the earth or about stars in general; and yet our present science has not developed far enough to tell us exactly what the state of the earth must have been a billion years ago. There may be a certain sense in which this question, too, may be unanswerable. For science will, perhaps, never get so far that it really can answer all the different questions which might be asked in regard to the state of the earth at that time. ”

“ None of us, I expect, knows the answer, but we have no doubt that in some future time the answer will be known. Most of us also believe that if there were some one who really knew all the facts and had the ability of drawing the proper conclusions he would be in a position to answer this question even now. This means that we do not regard such a question as unanswerable. We do not happen to know the answer, but we believe that the finding of it is in no way beyond human possibilities. ”

“ Usually both parties admit the existence of a certain boundary which walls in everything that is knowable by experience and separates it from the rest of the world. But the metaphysician believes that this wall can be scaled by our reason, while the empiricist believes this to be impossible and regrets it. ”

“ This question, therefore, belongs to the second group; philosophers have always worried about it. In most philosophies there are problems of this kind: certain questions within them are believed to “pass our understanding” or to be mysteries which we cannot fathom.
Our “Philosophy of Experience” takes an entirely different attitude. In order to understand it let us ask: “What is the criterion by which we decide whether an ‘insoluble’ problem belongs to the first or to the second group?” ”

“ Strict logical analysis has shown that there is the greatest imaginable difference. It is simply this, that empirical propositions really deal with something in the universe, they communicate actual facts, while mathematical propositions do not deal with anything real. “Numbers” cannot be found anywhere in the real world in the same way in which San Francisco can be found there. ”

“ We must draw conclusions from our knowledge of stars that have developed. By such observations, combined with our knowledge of the laws of nature, this question can be answered more and more definitely. ”

“ The difference between the two groups is this, that in the first one we can at least imagine means of finding a solution, even if these means exist nowhere in the world, whereas in the case of philosophical impossibility no imagination can bring us nearer to the answer; there are no ways on which even imagination could try to reach the goal. We cannot imagine what we would have to do or what would have to happen in the world in order to lead us to the answer of our former question: “How can a sensation arise from motions of molecules of the brain?” ”

“ Many thinkers believe that such problems and such solutions exist; the field beyond experience with which these questions and answers are concerned would be the field of “Metaphysics”, and the criterion which would assure us of the truth of those answers woud not be experience, but “reason.” The philosophers who believe that there are such truths which cannot be accounted for by experience but rest on reason, are called rationalists (ratio = reason) , and it is natural for them to think that all the most fundamental philosophical truths are of this kind. ”

“ It is also not true that numbers are simply imaginations of the human mind, like dragons or angels, and it is not true that, together with other “unreal” objects, they belong, to a world of their own, which Plato called the realm of Ideas, and in which many present day philosophers also believe, giving different names to it. ”

“ The skeptic also believes that he can answer a good many questions, at least in every day life, and he really has no serious intention of denying absolutely everything; and the dogmatist, we may be sure, cannot help but feel certain doubts in his mind and in his heart. He does not really believe that everything can be answered satisfactorily.
Most philosophies, therefore, take their position somewhat between those two extremes. They do not assert that all questions can be answered and they do not believe that no problem can be solved. ”

“ Just one more question with which to end up, and which is also typical. “Have animals consciousness?” Most of us think “Yes, of course; a dog is in many respect almost like a human being. How could this be if it did not have sensations and feelings?” Yet there has been a very enlightened philosopher, Descartes, who held the view that consciousness was something reserved for human beings, and that all animals were automata. Their behaviour should be regarded as mechanical reactions on certain stimuli without the intervention of any “consciousness.” ”

“ This may interest the scientist, but the philosopher is not concerned with it, he is worried by the other group of problems: those which are insoluble in principle: the reason why they cannot be solved is not an accidental state of affairs in the universe, but it seems to lie deeper; in this second case we speak of a philosophical or logical impossibility. ”

“ They all believe that a certain boundary exists between those problems to which we can find the final clues and those for which a solution seems to be forever impossible. The place where they draw the boundary line between that which can be known and that which cannot be known is, as I hinted before, one of the most characteristic traits of different philosophies. ”

“ Most of the older empiricists, it is true, denied the possibility of metaphysics with the same emphasis as we do, but, as I said before, not quite without a feeling of regret, because in their minds this meant a limitation of human knowledge, and consequently their attitude could justly be called skeptical (I may mention the names of Sextus Empiricus and of David Hume here) . ”

“ He believed that there was a real contradiction between these two proofs, which could be overcome only by his own philosophy with its distinction between the world as appearance and the world as reality. Again modern scince, discarding entirely Kant's merely speculative reason, has very definite arguments in favor of the view that the universe is finite in space. ”

“ And we may even go further and say that the same argument applies to human beings, for although we seem to know when we look into ourselves that we ourselves possess consciousness, how can we be sure about our fellow beings? Descartes thought there was a better argument for human beings possessing a soul than animals, because the existence of other consciousnesses is always infered by analogy, and there is a closer analogy between myself and other human beings than there is between human beings and animals. ”

“ The skeptic doubts everything, and the dogmatist does not suffer his fundamental beliefs to be touched by any doubt. Neither of these two philosophies, the skeptical or the dogmatic, really needs to be taken too seriously. ”

“ There are in the first place astronomical reasons which give a certain probability to this view, but there are also general reasons derived from the application of modern physics to problems concerning the structure of the universe which seem almost inevitably to lead to the conclusion that the universe must be finite in space, though probably not in time. ”

“ The chief problem of so-called metaphysics is supposed to be the question “What is the essence of Reality? Is the world essentially mental? Is it mind, as was taught by Berkeley, or is it matter as was taught by the materialists, or is it something which cannot be known, as Kant's ‘thing in itself’?” Thus, while most of the older philosophers seemed to have little difficulty in solving the problem, Kant maintained most emphatically that there was no solution to any metaphysical problem, i. ”

“ They are concerned with symbols, not with reality. They are nevertheless in a certain sense applicable to the world of facts, because symbols (words, letters, etc.) are used in speaking about facts. In short, they speak of reality, but they do not say anything about it. ”

“ It is true they have the io grammatical form of questions, and in many cases it is very hard to distinguish them from real ones, but a close scrutiny of the words which occur in the question, and of the way in which they are combined shows that they violate the rules of logical grammar and therefore make no sense at all. ”

“ This case is similar to the one of the former question in that the problem seems to be shifted from the realm of philosophical speculation to that of scientific observation, thereby changing from an apparently hopeless issue into a perfectly answerable question. With the development of our knowledge we come to see possibilities which formerly were not known to men ”