I raised this question incidentally only; it deserves to be thought about; but I do not want to be dragged too far from my subject. Is it possible that the contradictions of geologists never lead scientists to conclude the evolution of laws? Let us first observe that it is only in the youth of the Science that they employ the reasonings by analogy for which present geology is obliged to be satisfied. As it develops, it comes closer to the state that astronomy and physics seem to have already reached and where laws are likely to be stated in mathematical language. That day, what we said at the beginning of this work, will become true again without restriction. But many people think that all sciences are called to undergo more or less quickly, and one after another, the same evolution. If this were so, the difficulties that might arise would be only temporary, they would be destined to vanish as soon as the sciences had emerged from childhood.
But we do not need to wait for this uncertain future. What is geologist’s reasoning by analogy? A geological fact seems to him so similar to a present fact that he can not attribute this similarity to chance. He thinks he can explain it only by supposing that these two facts have occurred under exactly the same conditions. And he would imagine that the conditions were identical, except that point of detail that the laws of nature had varied in the interval, the whole world would have changed completely to the point of becoming unrecognizable. He would affirm on the one hand that the temperature must have remained the same, whereas, as a result of the upheaval of all physics, the effects of temperature would have become quite different, so that the very word of temperature would have lost all sense. Of course, whatever happens, it will never be with such a conception that it will stop. The way he conceives logic is absolutely opposed to it.