Methods, it can truly be said that they completely fail to hit the mark they are aimed at, that instead of proving that the conclusion reached by means of them is the only hypothesis that can explain the facts, they only prove that it does explain the facts, leaving the question forever open as to whether another might not do it equally well. "Such and such are the facts, what do they imply?" That is a type of the questions which all inductive reasoning undertakes to answer, all reasoning which attempts to take us from facts assumed to be known to others that are unknown. "These facts imply thus and so, because that supposition explains them." That is a type of the answers which inductive reasoning makes to all the questions propounded to it.
In the case of many of the theories of science, it appears to me that this cannot possibly be denied. Of the undulatory theory of light, the doctrine of evolution, the various conclusions of geology, for example, no one can claim more than that they are hypotheses that explain the facts more or less perfectly. Now I maintain that the difference between the proof of theories such as these and any so-called more thoroughly established conclusions of science, is not a difference in kind. It is merely a difference in the ease with which the imagination conceives other causes that may have produced the facts in question. As science accepts its conclusions in these cases as true, not because the scientific intellect sees that no other hypothesis can explain the facts, but because scientific common sense, so to say, brushes aside other hypotheses as improbable, so in the case of the so-called more thoroughly established conclusions of science, the scientific intellect accepts them as thoroughly established, not because it sees that other hypotheses cannot explain the facts, but because scientific common sense brushes aside as impossible any other hypotheses that can be suggested. What I am trying to say is, that the difference between conclusions more or less well established, provided they explain all the known facts, is not at all a difference in the evidence as apprehended by the pure intellect, the intellect uninfluenced by the emotional, instinctive side of the
