[40]. I have based this sketch on an attractive and illuminating account of his own development written by Professor Vaihinger for Dr. Raymund Schmidt’s highly valuable series, Die Deutsche Philosophie der Gegenwart in Selbstdarstellungen (1921), vol. II.
[41]. “Most workers on the problem of atomic constitution,” remarks Sir Ernest Rutherford (Nature, 5th August, 1922), “take as a working hypothesis that the atoms of matter are purely electrical structures, and that ultimately it is hoped to explain all the properties of atoms as a result of certain combinations of the two fundamental units of positive and negative electricity, the proton and electron.”
[42]. Havelock Ellis, Studies in the Psychology of Sex, vol. I.
[43]. Otto Rank, Der Künstler: Ansätze zu einer Sexual Psychologie.
[44]. The sexual strain in the symbolism of language is touched on in my Studies in the Psychology of Sex, vol. V, and similar traits in primitive legends have been emphasised—many would say over-emphasised—by Freud and Jung.
[45]. Einstein, in conversation with Moszkowski, expressed doubt as to the reality of Leonardo’s previsions of modern science. But it scarcely appeared that he had investigated the matter, while the definite testimony of the experts in many fields who have done so cannot be put aside.
[46]. For the Italian reader of Leonardo the fat little volume of Frammenti, edited by Dr. Solmi and published by Barbèra, is a precious and inexhaustible pocket companion. For the English reader Mr. MacCurdy’s larger but much less extensive volume of extracts from the Note-Books, or the still further abridged Thoughts, must suffice. Herbert Horne’s annotated version of Vasari’s Life is excellent for Leonardo’s personality and career.
[47]. Morley Roberts, who might be regarded as a pupil in the school of Leonardo and trained like him in the field of art, has in various places of his suggestive book, Warfare in the Human Body, sprinkled irony over the examples he has come across of ignorant specialists claiming to be men of “science.”
[48]. Needless to say, I do not mention this to belittle Galton. A careful attention to words, which in its extreme form becomes pedantry, is by no means necessarily associated with a careful attention to things. Until recent times English writers, even the greatest, were always negligent in spelling; it would be foolish to suppose they were therefore negligent in thinking.
[49]. Darwin even overestimated the æsthetic element in his theory of sexual selection, and (I have had occasion elsewhere to point out) unnecessarily prejudiced that theory by sometimes unwarily assuming a conscious æsthetic element.