There are several other alleged homologues or rudiments which are supposed to connect man with the lower animals, but which, whatever may be the resemblances, it is not necessary to discuss in detail, because there is one consideration at least which applies to the whole of this class of proofs, and to that I now pass. The three great classes of facts on which the whole argument rests, viewing man as an animal and omitting all reference to his intellect, are the resemblances of his bodily structure to that of the other mammals, the similarity between his embryonic development and theirs, and the rudiments. I reserve for separate discussion the counter-proof which may be derived from the nature of the human mind, and the special adaptation of the human structure to become the temporary residence and instrument of a spiritual and immortal being. "It is," says Mr. Darwin, "no scientific explanation to assert that they have all [man and the other animals of the mammalian class] been formed on the same ideal plan."[51] The similarity of pattern is pronounced "utterly inexplicable" upon any other hypothesis than that all these animals are descended from a common progenitor, and that they have become what they are by subsequent adaptation to diversified conditions. I may incur some risk in undertaking to suggest what is a "scientific" explanation. Certainly I do not propose to "assert" anything. But I will endeavor to keep within the bounds of what I suppose to be science. I take that to be a scientific explanation which, embracing the important facts of natural history as the groundwork of the reasoning, undertakes to show the rationality of one hypothesis that differs from another, when the question is, Which has the greater amount of probability in its favor?