[These lectures were eventually delivered on January 4 and 7, 1862, and were well reported in the Edinburgh papers.  The substance of them appears as Part 2 in “Man’s Place in Nature,” the first lecture describing the general nature of the process of development among vertebrate animals, and the modifications of the skeleton in the mammalia; the second dealing with the crucial points of comparison between the higher apes and man, namely the hand, foot, and brain.  He showed that the differences between man and the higher apes were no greater than those between the higher and lower apes.  If the Darwinian hypothesis explained the common ancestry of the latter, the anatomist would have no difficulty with the origin of man, so far as regards the gap between him and the higher apes.

Yet, though convinced that] “that hypothesis is as near an approximation to the truth as, for example, the Copernican hypothesis was to the true theory of the planetary motions,” [he steadfastly refused to be an advocate of the theory,] “if by an advocate is meant one whose business it is to smooth over real difficulties, and to persuade when he cannot convince.”

[In common fairness he warned his audience of the one missing link in the chain of evidence—­the fact that selective breeding has not yet produced species sterile to one another.  But it is to be adopted as a working hypothesis like other scientific generalisations,] “subject to the production of proof that physiological species may be produced by selective breeding; just as a physical philosopher may accept the undulatory theory of light, subject to the proof of the existence of the hypothetical ether; or as the chemist adopts the atomic theory, subject to the proof of the existence of atoms; and for exactly the same reasons, namely, that it has an immense amount of prima facie probability; that it is the only means at present within reach of reducing the chaos of observed facts to order; and lastly, that it is the most powerful instrument of investigation which has been presented to naturalists since the invention of the natural system of classification, and the commencement of the systematic study of embryology.”

[As for the repugnance of most men to admitting kinship with the apes,] “thoughtful men,” [he says,] once escaped from the blinding influences of traditional prejudices, will find in the lowly stock whence man has sprung the best evidence of the splendour of his capacities; and will discern, in his long progress through the past, a reasonable ground of faith in his attainment of a nobler future.”

[A simile, with which he enforced this elevating point of view, which has since eased the passage of many minds to the acceptance of evolution, seems to have been much appreciated by his audience.  It was a comparison of man to the Alps, which turn out to be] “of one substance with the dullest clay, but raised by inward forces to that place of proud and seemingly inaccessible glory.”