point of view, this question may seem unanswerable. There may be no means, as far as our human possibilities go, of ever finding out what Napoleon did at that moment. But although in one sense of the word this question is perhaps unanswerable, we do not get excited about a problem of this kind; the impossibility, if it should be impossible to solve the problem, is not one of very serious nature, because it would not be an intrinsic impossibility. It always remains possible, e. g. that a document might be found which tells us what Napoleon did at that particular time, or from which it could be infered in some indirect way.
Let us quickly look at some other questions. Geologists ask, “What was the earth like a billion years ago?” There were surely no historians there to tell us about the state of the earth at that time, and if we can ever find it out it will have to be in some indirect way. 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. 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.
Let us go on to some other question. “What is the substance of a distant star?” I take this particular question on purpose, because there was a French philosopher, August Comte, the exponent of Positivism, who expressed his belief that it could never be known of what substances distant stars consisted. Nowadays we have spectral analysis which allows us to make very definite statements about the chemical elements and their physical conditions which form the material of suns that are thousands of light-years distant from the earth. This is a good example of a problem that was pronounced insoluble by a leading philosopher, but was, only a short time afterwards, completely mastered by science.
Take another problem. “Is the universe finite or infinite in space and in time?” This used to be a typical philosophical question. It played
