Hiro Hirai argues that for Jacob Schegk (1511-1587), a friend of Philip Melanchthon and professor of philosophy and medicine at the University of Tübingen, the natural force of life or secondary causality present within created things is explicable in the Galenic terms of a “moulding” or “plastic faculty.” This power is controlled and determined by God but possesses its own energy. Where Medievals spoke of the vegetative power as a passive potency, Schegk combined the natural philosophy of Galen with the Neoplatonic principle of “spiritual vehicles” to argue that the plastic faculty is a quasi-intellectual energy (energeia) that denotes the principle of generation in natural beings. Hirai explains the difference between this faculty and the generative potency of the human soul:
Before closing his discussion, Schegk enumerates four possible opinions on the origin of human souls: 1) They are eternal and enter bodies at birth and leave them at death (according to Plato and Aristotle); 2) they are created all at once in the beginning of the world, but each of them enters its specific body at a precise moment; 3) they are drawn from the potentiality of matter by the plastic logos as the products of Nature; 4) each of them begins to exist by divine creation at the same moment when body is formed by the plastic logos. Schegk obviously chooses the last option, denying that the human soul is drawn from the potentiality of matter. Invoking the authority of the Bible, he concludes that God forms creatures by the plastic instrument of the seed’s nature, whereas only for man God simultaneously creates his soul by Himself and forms his organic body by means of this plastic nature. According to Schegk, God is the Creator of angels whereas the human soul, which shares the angelic essence, is created as the “breath” (spiraculum) of the Creator and is not “produced” by the plastic nature. The everyday creation of the human soul with the formation of its organic body, which is to be animated by this soul, is the ultimate action of the Creator. Although God attributed a primary generative task to the plastic nature, he does not cease to create human souls in order to show that man is not the “product” (plasma) of Nature but the son of God. Schegk concludes:
“I believe that, if the philosophers had known the Creator God, they would have agreed with us and would have said that the souls are not contained in the seed and in the seminal liquid of the male before they inform human bodies. In fact,denying the Creator God, or rather being ignorant of Him, they were forced to conclude that, by the spermatic logos , the human soul and its body are generated at the same time and that the human soul is not introduced from outside but is drawn from the potentiality of matter.”
For Schegk, the plastic nature produces all except the human soul, which, endowed with angelic essence, has only the Creator God as its maker. The human soul, or more precisely, the intellect cannot be generated through seminal propagation since it is something “born before” (progenes) Nature. It should be created by what precedes it. That is the Creator God.
~ Hiro Hirai, “The Invisible Hand of God in Seeds: Jacob Schegk’s Theory of Plastic Faculty,” Early Science and Medicine 12 (2007), 401, 402.
According to Hirai, Schegk’s De plastica seminis facultate (Strasburg, 1580) was the first Renaissance work to use the phrase “plastic faculty.” The idea of the plastic power went on to become a staple in 17th century works of medicinal science and natural philosophy. Perhaps its most important exponent was Ralph Cudworth, who used the concept of the “plastic nature” as an integral part of this enterprise to wed Platonism and atomism and whose use of the phrase would be influential for G.W. Leibniz.