31. However, with due deference to so many and such learned Doctors, I hardly see how their opinion can bear examination. For, as Pererius truly observes in his _Commentary on the Genesis_, chapt. 6, the whole strength and efficiency of the human sperm reside in the spirits which evaporate and vanish as soon as issued from the genital vessels wherein they were warmly stored: all medical men agree on that point. It is consequently not possible that the Demon should preserve in a fit state for generation the sperm he has received; for it were necessary that whatever vessel he endeavoured to keep it in should be equally warm with the human genital organs, the warmth of which is nowhere to be met with but in those organs themselves. Now, in a vessel where that warmth is not intrinsical but extraneous, the spirits get altered, and no generation can take place. There is this other objection, that generation is a vital act by which man, begetting from his own substance, carries the sperm through natural organs to the spot which is appropriate to generation. On the contrary, in this particular case, the introduction of sperm cannot be a vital act of the man who begets, since it is not carried into the womb by his agency; and, for the same cause, it cannot be said that the man, whose sperm it was, has begotten the fetus which proceeds from it. Nor can the Incubus be deemed its father, since the sperm does not issue from his own substance. Consequentially, a child would be born without a father, which is absurd. Third objection: when the father begets in the course of nature, there is a concurrence of two causalities: the one, material, for he provides the sperm which is the matter of generation; the other, efficient, for he is the principal agent of generation, as Philosophers agree in declaring. But, in this case, the man who only provided the sperm would contribute but a mere material, without any action tending to generation; he could therefore not be regarded as the father of the child begotten under those circumstances; and this is opposed to the notion that the child begotten by an Incubus is not his son, but the son of the man whose sperm the Incubus has taken.