Thursday, August 11, 2011

Medieval genetics

Catholic epologists often make a big deal about the (alleged) fact that it wasn’t until the 20C that Protestants began to support contraception. Of course, even if that’s true, there’s an obvious reason for that: the availability of safe, effective birth control is contingent on advances in medical science.

By the same token, Catholic epologists have a habit of defaulting to traditional conclusions regarding birth control while ignoring the obsolete “science” that underlay traditional conclusions. For instance, consider the understanding of genetics reflected in Aquinas, who is summarizing various traditional positions, before stating his own:

Reply to the Ninth Objection. There are several opinions about the life of the embryo. According to some in human generation the soul, like the human body, is subject to stages of progression, so that as the human body is virtually in the semen, yet has not actually the perfection of a human body by having distinct members, but gradually reaches this perfection through the force of the semen, so at the beginning of the generation the soul is there having virtually all the perfection which subsequently is to be seen in the perfect human being, yet it has not this perfection actually, since there is no sign of the soul’s activity, but attains thereto by degrees: so that at first there are indications of the action of the vegetal soul, then of the sensitive soul, and lastly of the rational soul. Gregory of Nyssa mentions this opinion (De Homine): but it cannot be admitted. It means either that the soul in its species is in the semen from the very . outset, deprived however of its perfect activity through lack of organs, or that from the beginning there is in the semen some energy or form not having as yet the species of a soul (just as the semen has not as yet the appearance of a human body) but by the action of nature gradually transformed into a soul at first vegetal, then sensitive and lastly rational. The former alternative is rebutted first by the authority of the Philosopher. He says, in fact (De Anima ii, i), that when we say that the soul is the act of a physico-organic body which has life potentially we do not exclude the soul, as we exclude it from the semen and the fruit. Hence we gather that the semen is animated potentially in that the soul is not therein. Secondly, because as the semen has no definite likeness to the members of the human body (else its resolution would be a kind of corruption) but is the residue of the final digestion (De Gener. Anim. i, 19), it was not yet while in the body of the begetter perfected by the soul, so that in the first instant of its separation it could not have a soul. Thirdly, granted that it was animated when it was separated, this cannot refer to the rational soul: because since it is not the act of a particular part of the body, it cannot be sundered when the body is sundered.
The second alternative is also clearly false. For seeing that a substantial form is brought into act not continuously or by degrees but instantaneously (else movement would needs be in the genus of substance just as it is in that of quality) the force which from the outset is in the semen cannot by degrees advance to the various degrees of soul. Thus the form of fire is not produced in the air so as gradually to advance from imperfection to perfection, since no substantial form is subject to increase and decrease, but it is the matter alone that is changed by the previous alteration so as to be more or less disposed to receive the form: and the form does not begin to be in the matter until the last instant of this alteration.
Others say that in the semen there is at first the vegetal soul and that afterwards while this remains the sensitive soul is introduced by the power of the generator, and that lastly the rational soul is introduced by creation. So that they posit in man three essentially different souls. Against this, however, is the authority of the book De Ecclesiasticis Dogmatibus (xv): “Nor do we say that there are two souls in one man as James and other Syrians write; one, animal, by which the body is animated and which is mingled with the blood, the other spiritual, which obeys the reason.” Moreover, it is impossible for one and the same thing to have several substantial forms ! because, since the substantial form makes a thing to be, not in this or that way, but simply, and establishes this or that thing in the genus of substance; if the first form, does this, the second form at its advent will find the subject already established with substantial being and consequently win accrue to it accidentally: and thus it would follow that the sensitive and rational souls in man would be united accidentally to the body, Nor can it be said that the vegetal soul which is the substantial form in a plant is not the substantial form in a man, but a mere disposition to the form, since that which is in the genus of substance cannot be an accident of anything.
Hence others say that the vegetative soul is potentially sensitive and that the sensitive soul is its act: so that the vegetative soul which at first is in the semen is raised to the perfection of the sensitive soul by the action of nature; and further that the rational soul is the act and perfection of the sensitive soul, so that the sensitive soul is brought to its perfection consisting in the rational soul, not by the action of the generator but by that of the Creator. Hence they hold that the rational soul is in man partly from within, namely as regards its intellectual nature, and partly from without as regards its vegetative and sensitive nature. Now this is altogether impossible, because either it means that the intellectual nature is distinct from the vegetal and sensitive souls, and thus we return to the second opinion, or it means that these three natures constitute the substance of the soul wherein the intellectual nature will be the form as it were, and the sensitive and vegetative natures, matter. From, this it would follow, as the sensitive and vegetative natures are corruptible through being educed from matter, that the substance of the rational soul would not be immortal. Moreover, this opinion is involved in the same impossibility as we have shown to be implicated in the first opinion, namely that a substantial form be brought into act by degrees.
Others say that there is no soul in the embryo until it is perfected by the rational soul, and that the vital functions to be observed therein proceed from the soul of the mother. But this also is impossible: because living and non-living things differ in that living things are self-moving in respect of vital functions, whereas non-living things are not. Wherefore nutrition and growth which are the functions proper to a living being cannot result in the embryo from an extrinsic principle such as the mother’s soul. Moreover, the mother’s nutritive power would assimilate food to the mother’s body and not to the body of the embryo: ‘since nutrition serves the individual just as generation serves the species. Further, sensation cannot be caused in the embryo by the mother’s soul. Wherefore others say that there is no soul in the embryo before the infusion of the rational soul, but that there is a formative force that exercises these vital f~nctions in the embryo. This again is impossible, because before the embryo attains to its ultimate complement it shows signs of various vital functions; and these cannot be exercised by one power: so that there must needs be a soul there having various powers.
We must therefore say differently that from the moment of its severance the semen contains not a soul but a soul power: and this power is based on the spirit contained in the semen which by nature is spumy and consequently contains corporeal spirit. Now this spirit acts by disposing matter and forming it for the reception of the soul. And we must observe a difference between the process of generation in men and animals and in air or water. The generation of air is simple, since therein only two substantial forms appear, one that is voided and one that is induced, and all this takes place together in one instant, so that the form of water remains during the whole period preceding the induction of the form of air; without any previous dispositions to the form of air. On the other hand in the generation of an animal various substantial forms appear: first the semen, then blood and so on until we find the form of an animal or of a man. Consequently this kind of generation is not simple, but consists of a series of generations and corruptions: for it is not possible, as we have proved above, that one and the same substantial form be educed into act by degrees. Thus, then, by the formative force that is in the semen from the beginning, the form of the semen is set aside and another form induced, and when this has been set aside yet another comes on the scene, and thus the vegetal form makes its first appearance: and this being set aside, a soul both vegetal and sensitive is induced; and this being set aside a soul at once vegetal, sensitive and rational is induced, not by the aforesaid force but by the Creator. According to this opinion the embryo before having a rational soul is a living being having a soul, which being set aside, a rational soul is induced: so that it does not follow that two souls are together in the same body, nor that the rational soul is transmitted together with the body.
Reply to the Tenth Objection. Before the advent of the rational soul the embryo is not a perfect being but is on the way to perfection: and therefore it is not in a genus or species save by reduction, just as the incomplete is reduced to the genus or species of the complete.
Reply to the Eleventh Objection. Although the soul is not in the semen from the beginning, the soul-force is there, as stated above, which force is based on the spirit contained in the semen; and is called a soul-force because it comes from the soul of the generator.
Reply to the Twelfth Objection. Before the advent of the rational soul the semen is a living and animate being, as stated above; wherefore we grant this argument.
The same answer applies to the Thirteenth, Fourteenth and Fifteenth Objections.
Reply to the Sixteenth Objection. The formative force that is from the outset in the semen remains even after the advent of the rational soul; just as the animal spirits remain into which nearly the whole substance of the semen is changed. This force, which at first served to form the body, afterwards regulates the body. Thus heat which at first disposes matter to the form of fire remains after the advent of the form of fire as an instrument of the latter’s activity.

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