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I. The Text, from Summa theologiae I.75.1c: "Whether the soul is a body."
II. Aquinas' Argument in Syllogistic Form:
Major: The first principle or formal cause of life of those things which live cannot be corporeal (No M is P).
Minor: The soul (anima) is the first principle of life of those things which live (S is M).
Conclusion: Therefore, the soul is not corporeal (No S is P).
Proof of the Major: Although a body may be a principle or formal cause of life, as the heart is a principle of life in an animal, it cannot be the first principle of life. For it is clear that to be a principle of life, or to be a living thing, does not belong to a body due [merely] to the fact that it is a body; since, if that were the case, every body would be a living thing, or a principle of life. Therefore a body is competent to be a living thing or even a principle of life, as "such" a body [i.e., a specific kind of body]. Now that it is actually such a body, it owes to some principle which is called its act (form); thus heat, which is the principle of calefaction, is not a body, but an act (form) of a body.
Proof on the Minor: This is the definition of 'soul'. Explanation: "... principle of life": Life is shown principally by two actions, knowledge and movement; now, we call these things (that exhibit knowledge and movement) "animate" (animata) [i.e. having a soul], and those things which do not, "inanimate" (inanimata). "First principle...": It is manifest that not every principle of vital action is a soul (for then the eye would be a soul, as it is a principle of vision; and the same might be applied to the other instruments of the soul) but it is the "first" principle of life, which we call the soul. Therefore, the first principle of life is the soul.
And the conclusion follows: The soul is incorporeal; it is not a body, but the first act (or substantial form) of any living body.
5 comments:
Thanks for breaking this down. What translation is that?
Regarding the proof of the major: For it is clear that to be a principle of life, or to be a living thing, does not belong to a body due [merely] to the fact that it is a body; since, if that were the case, every body would be a living thing, or a principle of life.
How would you prove—contrary to materialism, physicalism, panpsychism, etc.—that every body is not "a living thing, or a principle of life"? Thanks
Ryan: This is the translation by the Dominican Fathers of the English Province (available at www.summatheologiae.com), but with some corrections of my own.
Alan: Panpsychism precisely holds that "every body is a living thing or a life principle." So it makes sense that I would have to argue against that view. But materialism and physicalism do not hold that; so I'm not sure why I would have to argue against them in that regard.
In any case, an argument against panpsychism could be:
Major: All living organisms are substances that 'move themselves intrinsically (sese movent ab intrinseco) according to their nature and conserve themselves in their perfection'--viz., substances that perform the intrinsic motions of nutrition and reproduction (cf. Hugon, Cursus philosophiae thomisticae, II-II, Tract. I, Art. II, n. III.).
Minor: Not all things are substances that 'move themselves intrinsically according to their nature and conserve themselves in their perfection'--viz., substances that perform the intrinsic motions of nutrition and reproductions.
Conclusion: Therefore, not all things are living organisms.
Against materialism/physicalism, I believe it suffices to say:
P1: If matter alone were capable of conserving the substantial unity of a living thing, then every body would be alive.
P2: If matter alone cannot conserve the substantial unity of a living thing, then some formal cause is required for a living organism to conserve its substantial unity.
P3: But not every body is alive.
Conclusion: Therefore, some formal cause is necessary for a living organism to conserve its substantial unity--and we call this formal cause of living organisms 'the soul'.
Good stuff! Thanks.
Regarding the premise " since, if that were the case, every body would be a living thing, or a principle of life" and in the your comment "P1: If matter alone were capable of conserving the substantial unity of a living thing, then every body would be alive."
I'm not sure how these are sufficient or evident.
[Thomas uses the term "body", so obviously the discussion here is about a "material" matter-form composite.]
Why would *every* body be a living thing or a principle of life? What if a scientist claimed that only *certain* bodies were principles of life, and thus some bodies have life (e.g. animals) and others are inanimate (e.g. rocks). For instance, some might claim that DNA or amino acids, or what have you, is the material principle. Then things that have DNA and any other material requisites would be alive and things that didn't wouldn't.
I hope this is clear. Thanks!
Apparently St. Thomas disproves panpsychism in Summa Theoligica Ia q. 18 a. 1.
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