Chapter 6: Daniel Sennert and His Seminal Principle

[following is a chapter summery of Hiro Hirai’s book, Medical Humanism. Quotations are all from the primary sources quote in the book]

Daniel Sennert (1572-1637), a professor of medicine at University of Louvain worked largely on the early seventeenth-century intersection of matter theory and life sciences, focusing on and developing a corpuscular interpretation of the origin of life to explain biological, normal generation (univocal generation) as well as spontaneous generation (equivocal generation). This chapter examines the univocal generation first and then his theory of spontaneous generation, which Sennert argues along with Liceti that there is no such thing as strictly speaking abiogenesis.

Sennert first asks whether souls can be produced. He answers in the negative, and argues that souls are multiplied but not produced or generated. This is because for him souls can be (and were) created by God at the beginning, and God as the first and universal cause is the only agent who can create souls. Having ordained nature to perpetuate the course of generation and corruption, God gave the second causes a capacity to produce the generation of all things from the very first soul simply by multiplying themselves. This is an argument against those who hold the eduction of forms – for even if forms are drawn out from the potentiality of matter, the question of where they originate is left entirely unanswered. For this reason, Sennert advances the idea that all forms can multiply, just as is read in Genesis: “Be fruitful and multiply.” That is why he thinks that souls are not produced anew but are only multiplied in the generation of natural beings. Further, he also differs from Liceti with regard to the forms in that while the latter taught that forms are generated from a certain “rudiment” of form preexisting in matter, Sennert does not accept the idea that the form, first possessing a generic nature, then receives its own specificity from an external agent, and criticizes the opinion since Liceti did not reveal what this rudiment really is.

For Sennert, a simple quality like heat cannot produce a form, which is a divine substance. He thus concludes that besides the disposition of matter something formal is needed in the seed as the cause of its action.

Now for Sennert, the plastic faculty is equated with the soul itself, which is for Schegk that which is introduced from the heaven after the pure motion exerted from the male parent to communicate the spermatic/plastic faculty into the matter. This spermatic faculty, for Schegk, is replaced by the human soul that already preexists, and disappears after this replacement with the soul. But, Sennert asks, if the spermatic faculty gets replaced with the soul, and acts like the soul itself, why not call this spermatic faculty a soul, without introducing unnecessary terms such as plastic faculty, spermatic faculty, instrumental potentiality and productive actuality, etc? For Sennert, this plastic faculty, or the plastic reason-principle, is identical to the soul, which is not the instrumental but the principal agent of generation.

So for Sennert, the seed is animate and possesses a soul in itself. “[I]t is a very simple substance or a certain spiritus, in which the soul and the plastic force immediately reside, and contains within itself the Idea of the organic body from which it has fallen, thus possesses the potentiality both to form an organic body similar to that from which it has fallen to prefect itself into an individual of the same species as [that] of the parent.” For Sennert, spiritus is not the principal cause of generation as it is for Fernel, but merely an instrumental cause of the soul. The soul uses the spiritus residing in the seed and, as far as the spiritus is in the seed, the soul is in its own subject. But when the spiritus goes away, the soul cannot remain in the seed anymore and the seed becomes sterile. Further, Sennert makes a radical break from the traditional thinkers in that Sennert recognizes only one soul throughout – the humans have from the beginning one rational soul, which has the vegetative, sensitive and intellectual faculties, which is transmitted through the seed.

Spontaneous Generation

Sennert argues in the manner of Liceti that the equivocal generation too is realized by an internal principle lying hidden in matter, which does not differ from non-spontaneous generation in which the principle of generation is also hidden in matter and inaccessible to human sense-perception. Indeed, Sennert goes on to say that spontaneous generation too is caused by a univocal agent, for living beings that do not reproduce themselves through the seed in the literal sense still possess something that corresponds to the seed. This something contains not the soul but the principle or the form which begins to carry out the functions of the soul when it finds suitable matter. In this way, Sennert explains that every corpse of plants and animals can seemingly produce worms and maggots spontaneously, when in fact it is this particular form which will manifest itself as a soul in a certain condition. This is why Sennert explains that when Aristotle said “[t]here is water in earth, and pneuma in water, and in all pneuma is soul-heat, so that all things are in a sense full of soul,” Aristotle does not mean that all things are animate, but that there is in all things such a hidden entity which becomes manifest and executes the functions of life when it encounters suitable matter.

This hidden entity, which he calls a seminal force, is the internal principle of generation, i.e. seminal principle. But after a great change in matter, according to Liceti, because of the loss of the heat that sustains the soul, the soul degenerates into another inferior species. But Sennert does not accept the mutation of the form, and rather he opts for the multiplicity of the forms in a subject, calling the one dominant and the other(s) subordinate forms. When this dominant substantial form disappears, one of these subordinate substantial forms replaces it by taking over its functions. Sennert further argues that this seminal principle is present in a subject even if it is divided into the minima or smallest atoms, which further supports his view that all things are full of souls. So in the case of living beings that are seemingly spontaneously generated, their seminal force can persist even down to the level of atoms until the time when it finds a suitable matter from which it establishes an animate body. So the atoms of living beings are essentially corpuscles composed of primordial atoms for Sennert, and although the soul residing in one atom may be too weak to generate anything, several atoms can be united, which allows the souls contained therein to be gathered and become more powerful.

In recapitulation, whether it is called “seed,” “seminal principle,” or “soul,” there is first some entity that comes from the corpse of living beings and lies hidden in matter. So nothing is really generated spontaneously but everything is generated by its own soul or at least by this seminal principle which corresponds to the soul analogously. And when this entity is placed under suitable conditions, and stimulated by ambient heat, it begins to perform the functions of life.

The soul’s vehicle was no longer conceived as the spiritus itself but as an atom which is informed by its internal soul or the seminal principle corresponding by analogy to the soul, while the spiritus was clearly seen as being composed of atoms. So the Sennert’s idea of the seminal principle as the atom’s internal soul was made through his corpuscular reinterpretation of the soul’s vehicle. He then developed the idea of living corporeal corpuscles, which are scattered around the world and which carry the soul or the seminal principle, thus guaranteeing the continuous emergence of life. For Sennert, one atom, derived from living beings, has its own soul just as one atom of inorganic beings has its own form. Although Sennert borrowed the concept of the seminal principle from the concept of seeds, developed by a Paracelsian philosopher Severinus, it was Sennert who explicitly connected it to the atomism, hence playing the central role in understanding the development of matter theory in the advent of modern science. Thus, Hirai argues that Sennert is the great synthesizer of the concept of seeds with revived atomism, tracing back the origin of Gassendi’s idea to Sennert.

Sennert quoted in Hiro Hirai, Medical Humanism, 157. “…it is a vain fiction to say that the generic nature is a rudiment of form and, as it were, a semi-form. It would follow from this opinion that like does not generate its like. Since the specific form gives each thing its own nature but not a generic nature, if the parent should only provide the matter in which the generic form exists, i.e., a rudiment of form or a semi-form as Liceti says, then it would be an external agent like heat that would introduce the specific difference.”

Sennert quoted in Hiro Hirai, 159-160.

Sennert quoted in Hiro Hirai, 163. “…the soul can be in some matter after yet another way without informing or vivifying this matter this matter or providing the actions proper to this living being. Thus the seeds of plants and animals can reside in water and earth, the soul [can reside] in these [seeds] without informing or vivifying water or earth.”

Aristotle quoted in Hiral, 164. See also Sennert’s comment quoted on the same page. “To be sure, as Aristotle teaches, animal heat and especially that kind of heat that possesses the adjoined soul are truly in this whole part of the inferior world (earth, water and air). [They exist], however, not as their essential part or essential attribute because earth and water are cold by their nature and because neither earth nor water are informed by the soul. But [they are] as a thing put in a place or in a vessel, without doubt because earth, water and air contain the living beings’ corpses, parts and excrements in which there are atoms and corpuscles possessing a soul.”

Sennert quoted in Hiral, 169. “Indeed, the soul of one single atom is so weak and it can neither vivify and inform the matter of the mushroom nor perform what can be done by the souls, gathered from many [souls], of numerous atoms united into one body.”