Moritz Schlick

“ All great philosophical issues that have been discussed since the time of Parmenides to our present day are of one of two kinds; we can either give them a definite meaning by careful and accurate explanations and definitions, and then we are sure that they are soluble in principle, although they may give the scientist the greatest trouble and may even never be solved on account of unfavourable empirical circumstances, or we fail to give them any meaning, and then they are no questions at all. Neither case need cause uneasiness for the philosopher. ”

“ Why should Nature seem more wonderful to us if she cannot be known completely ? Surely she does not wish to conceal anything on purpose, for she has no secrets, nothing to be ashamed of. On the contrary, the more we know of the world the more we shall marvel at it ”

“ It seems a little ridiculous to suppose that a day might come when all imaginable problems would be solved, so that there would be no questions left for which the human mind would crave an answer. We feel sure that our curiosity will never be completely satisfied and that the progress of knowledge will not come to a stop when it has reached its last goal. ”

“ The final and perhaps the most important truths are thought to be permanently hidden from our eyes; the key to the Riddle of the Universe is believed to be buried in depths the access to which is barred to all mortals by the very nature of the Universe. ”

“ Nothing is gained by picturing God as jealously hiding from his creatures the innermost structure of his creation, indeed, a worthier conception of a Supreme Being should imply that no ultimate boundary should be set to the knowledge of beings to whom an infinite desire of knowledge has been given. The existence of an absolute ignorabimus would form an exceedingly vexing problem to a philosophical mind. It would be a great step forward in philosophy, if the burden of this bewildering problem could be thrown off. ”

“ A conscientious examination shows that all the various ways of explaining what is actually meant by a question are, ultimately, nothing but various descriptions of Ways in which the answer to the question must be found. Every explanation or indication of the meaning of a question consists, in some way or other, of prescriptions for finding its answer. ”

“ It is natural that mankind should take great pride in the steady advance of its knowledge. The joy we feel in the contemplation of scientific progress is fully justified. One problem after another is solved by science ”

“ Since only the latter kind of impossibility would have that hopeless and fatal character which is implied by the ignorabimus and which could cause philosophers to speak of a "Riddle of the Universe" and to despair of such problems as the "cognition of things in themselves", and similar ones, it would seem that the acceptance of my opinion would bring the greatest relief to all those who have been unduly concerned about the essential incompetence of human knowledge in regard to the greatest issues. ”

“ It is one of the most important contentions of the philosophy I am advocating that there are many questions which it is empirically impossible to answer, but not a single real question for which it would be logically-impossible to find a solution. ”

“ According to this common belief, there are many questions which we can formulate, and whose meaning we can grasp completely, though it is definitely impossible to know their answer which is beyond the natural and necessary boundary of all knowledge. In regard to these questions a final ignorabimus is pronounced. Nature, it is said, does not wish her deepest secrets to be revealed; God has set a limit of knowledge which shall not be passed by his creatures, and beyond which faith must take the place of curiosity. ”

“ But we cannot declare it impossbile in principle. The moon happens to be very far off; it happens to turn always the same side towards the earth; it happens to possess no atmosphere in which human beings could breathe — •but we can very easily imagine all these circumstances to be different. We are prevented from visiting the moon only by brute facts, by an unfortunate state of affairs, not by any principle by which certain things were deliberately withheld from our knowledge. ”

“ Obviously, men will never know the answers to these questions, however hard they may try. But at the same time, we know that they would never try very hard. These problems, they will say, are of no importance, no philosopher would Worry about them, and no historian or naturalist would care whether he knew the answers or not. ”

“ It is commonly assumed that there are other imperative reasons why scientific advance cannot go on for ever. Most people believe in the existence of barriers that cannot be scaled by human reason and by human experience. ”

“ This, one may argue, is evidently impossible, for without doubt there are unanswerable questions. It is very easy to ask questions the answers to which, we have the strongest reasons to believe, will never be known to any human being. ”