The doctrine that in sexual generation the semen furnishes soul and generative heat but none of the matter[416] of which the embryo consists, renders logical the view, which Aristotle would seem to hold, that it is soul from the air and generative heat from the sun which in spontaneous generation represent the derivatives from the male.[417] The presence about us of "the psychical principle," thus diffused, may well seem startling to a modern biologist; but we may remind ourselves that in ancient times many believed the soul to be conveyed by the air into even the higher animals; even into man himself, even man's "understanding" reaching him thus.[418] Indeed, not only the words "pneuma" and "spiritus," as we have learned, but also the Greek and Latin words for "soul," viz.: "psyche" and "anima," meant originally simply "breath." Let us recall the words of scripture, which seem so vivid to one who watches the change in a new-born child as the first breath is taken: "And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul."[419]
That the soul enters with the breath is, however, expressly denied by Aristotle. Conceding a share of soul to every living thing he points out quite simply that there are animals which do not breathe at all, to say nothing of plants.[420] Clearly, the doctrine which he rejects would be hard to reconcile with his theory of sexual generation, according to which theory the sensory soul, and in man even the divine intellectual soul, is potential in the semen and imparted thereby to the product of conception.[421] Indeed, there is a chapter of Aristotle's treatise On Soul in which he even seems to argue against the presence of soul in the air, in a polemic directed against those who believe the soul to be "composed of the elements."[422] In this polemic he is the subtle philosopher; but in his statements about generation he seems more the biologist; for in these his thought, if not more ripe, appears to be less concerned with disputation than with phenomena and the interpretation thereof.
The generation of living things is but generation still, whether it be sexual or spontaneous; and the modern student of general physiology may trace further parallels of thought in Aristotle's account of spontaneous generation and in those words of his about the semen which Harvey quotes and we have studied. That living rudiment, spontaneously generated, which consists of a foam-bubble whose film of earth and water was formed by the heat of the sun and includes air charged with generative heat associated with soul—surely that reminds one of the foamy semen, and of "the spirits included in the semen and in foaminess," and of that within the spirits "which makes semen generative, the so-called heat," the "nature which is analogous to the element of the stars," which nature is derived from the male parent and is associated with the soul potential in the semen. In the Greek text of Aristotle one and the same word, "pneuma" is used to express both the air in the foam-bubbles of spontaneous generation, and the vapor in the foam-bubbles of the semen. In translation "pneuma" must be rendered "spirits" in the case of the semen, and the verbal identity is lost which, by reason of the very vagueness of the Greek word, helps to mark the parallelism of thought. It is with pneuma, spirits, that the testicles and breasts are swollen at the advent of puberty,[423] according to Aristotle; and with the presence of pneuma he connects the pleasure of the sexual act.[424] We have found him laying stress upon the fact that "the nature of semen is foamy"—that its "generative medium ἡ γονή is foam": and he tells of the spontaneous generation of certain shellfish in a place where there is "foamy mud."[425] When he obscurely says that in the semen "the pneuma included in the semen and in foaminess"[426] is the vehicle of the generative heat, does not the turn of phrase indicate that Aristotle's thought is ranging far, that he is thinking not only of the foam of the semen but of other widely different kinds of prolific foam as well? Does he not seem to think that, in general, the power of bringing matter to life as a new individual dwells typically in a bubble representing earth, water, and air, and charged with soul and with generative heat, for the presence of which the sun is responsible, heat other than that of elemental fire?[320] It is not fanciful—for Aristotle himself, we remember, has done so incidentally—to connect such speculation with the ancient myth of Aphrodite, the goddess of love, who sprang from the foam which had risen upon the sea, about the immortal genitals of Uranus, which had been severed and cast therein; Uranus being the heavens personified.[427]
Before the time of Aristotle important thinkers had held the heavenly bodies, and even the heavens themselves, to be fire;[428] and we have seen that after his time Cleanthes did the same, simply setting apart the generative fire from the destructive. Aristotle denied that the sun is fire, though he could not have denied that its radiant generative heat produces no different sensation from that of sterile fire kindled upon earth. He did not identify the sun's heat with ether, the "body on high," though he styled the heat of the semen a "body" analogous to the ether. How then did Aristotle obtain heat from the ethereal sun? The point is crucial and he met it; but in so doing he revealed a very weak place in his towering fabric of speculation. In his treatise On Heaven, speaking of the heavenly bodies, he says:—
"The heat and light from these arise from the friction which the air undergoes by reason of their course. For it is the nature of motion to fire even wood and stone and steel."
He then speaks of projectiles, and says:—
"These, then, are heated because borne onward in air which becomes fire from the shock of the motion. But each of the bodies on high is borne onward in its sphere, so that they are not fired; while the air, being beneath the sphere of the circling body,[429] is heated of necessity as this [body] is borne onward, and mainly where the sun is set in place. Therefore, when the sun approaches and rises and is above us, heat is generated. Be it said, then, of the heavenly bodies, that neither are they fiery nor are they borne on in fire."[430]
In his Meteorology Aristotle boldly says: "The sun, which is held to be especially hot, appears white, but not to be like fire."[431]
Hardy thinker as he is, however, Aristotle nowhere undertakes to tell how the heat of friction between the air and the circling "first element" on high becomes generative, as opposed to the heat of friction between the air and a projectile composed of the lower elements. As to this the Aristotle who deals with the heavens does not strike hands with Aristotle the biologist; nor is light thrown by its author on the Aristotelian passage quoted by Harvey, in which alone does the generative heat of animals figure as "the nature which is analogous to the elements of the stars";[432] nor yet does the Aristotelian dictum that "Man and the sun generate man"[338] remain other than a great truth which awaits elucidation.
More than nineteen centuries after Aristotle's death Harvey published the following, in his treatise On Generation:—