Müller. For obscurantism is a sin, possibly not against the Holy Spirit, but yet against the human spirit, which one ought therefore never to forgive, but always and everywhere implacably to remember against whoever has been guilty of it, and take every opportunity of showing contempt for him so long as he lives, nay, after he is dead. But just as often the above result does not take place; for example, Kant's brother was quite an ordinary man. To explain this I must remind the reader of what is said in the thirty-first chapter on the physiological conditions of genius. Not only an extraordinarily developed and absolutely correctly formed brain (the share of the mother) is required, but also a very energetic action of the heart to animate it, i.e., subjectively a passionate will, a lively temperament: this is the inheritance from the father. But this quality is at its height only during the father's strongest years; and the mother ages still more quickly. Accordingly the highly gifted sons will, as a rule, be the eldest, begotten in the full strength of both parents; thus Kant's brother was eleven years younger than him. Even in the case of two distinguished brothers, as a rule, the elder will be the superior. But not only the age, but every temporary ebb of the vital force or other disturbance of health in the parents at the time when the child is begotten may interfere with the part of one or other, and prevent the appearance of a man of eminent talent, which is therefore so exceedingly rare a phenomenon. It may be said, in passing, that in the case of twins the absence of all the differences just mentioned is the cause of the quasi-identity of their nature.
If single cases should be found in which a highly gifted son had a mother who was not mentally distinguished at all, this may be explained from the fact that this mother herself had a phlegmatic father, and on this account her more than ordinarily developed brain was not adequately excited by a corresponding energy of the circulation – a necessary condition, as I have explained
