CHAPTER XLI—That the Variety of Creatures does not arise from any Contrariety of Prime Agents²⁶⁷²⁶⁷   St Thomas has seven chapters (XXXIX–XLV) discussing the variety of creatures, why the universe is not uniform but diversified, and how it has come to consist of such diverse components. As regards living creatures, the discussion is familiar to us from Darwin’s Origin of Species and the theory of Evolution. St Thomas ventures on a larger question, the origin of all species, inanimate as well as animate. He states and rejects various archaic theories; but the point of supreme interest to the modern mind is never raised. In all the seven chapters there is not one word pointing to evolution. I have been driven to make large omissions, omissions which I feel sure the Saint would have sanctioned, had he been face to face with the cosmogonies of our day. Life is short art is long: the ground of philosophy must not be cumbered with obsolete machinery.
   It is pleaded on St Thomas’s behalf that the question before him is a metaphysical one, independent altogether of the manner in which actual species have come into existence.

IF the diversity of things proceeds from diversity or contrariety of diverse agents, this would seem to hold especially of the contrariety of good and evil, so that all good things should proceed from a good principle, and evils from an evil principle. Now there is good and evil in all genera. But there cannot be one first principle of all evils: for the very essence of such a principle would be evil, and that is impossible. Everything that is, inasmuch as it is a being, must necessarily be good: for it loves and strives to preserve its own being, a sign whereof is this fact, that everything fights against its own destruction: now what all things seek is good. It is impossible therefore for the diversity of things to arise from two principles, one good and one evil.²⁶⁸²⁶⁸    Done into syllogistic form, the argument might stand thus:    What all things seek, even a principle of evil would seek.
   But all things seek their own self-preservation.
   Therefore even a principle of evil would seek its own self-preservation.
   Again,    What all things seek, is good.
   But self-preservation is what all things seek.
   Therefore self-preservation is good.
   But a principle of evil would seek its own self-preservation.
   Therefore a principle of evil would seek some good.
   But a principle of evil ought to be averse to all good.
   Therefore a principle of evil is absurd.
   One wonders whether this is the argument that St Thomas thought of at the table of St Louis, when he suddenly started up and cried, Ergo conclusum est contra Manichaeos. But it is difficult to kill a heresy with a syllogism. One might perhaps distinguish between absolute and relative good; and upon that distinction urge that the self-preservation, which the evil principle sought, was good relatively to it only, but evil absolutely for the world.
   The deepest flaw in the Manichean notion of an Evil Principle is that which is pointed out in the next argument (n. 9). Moreover every argument which establishes the unity and infinite perfection of God, is destructive of Manicheism. (Cf. Isaias xlv, 6, 7, quoted below.)
   Matter is not evil, as Plato supposed, but its essential capacities for good are greatly limited; and, where good stops short, evil readily enters in. God does not override essentialities.

9. What in no manner of way is, is neither good nor evil: while every thing that is, in so far as it is, is good. A thing can be evil therefore only inasmuch as it is not-being, that is, privative being;²⁶⁹²⁶⁹Ens privativum. A privation as distinguished from a mere negation, is the lack of a perfection due to the nature, as the lack of sense in this or that man, not the lack of wings. Privation is in the individual only, never in the species. Hence all evil is in the individual: the specific nature is entirely good. and the evil is precisely the privation. Now privation never comes of the ordinary action of any cause: because every cause acts inasmuch as it is endowed with ‘form’; and thus the ordinary effect of its action must also be endowed with ‘form,’ since every agent acts to the production of its own likeness, unless it be accidentally hindered. It follows that evil does not come of the ordinary action of any cause, but is accidentally incident among the effects of ordinary causation.²⁷⁰²⁷⁰The usual example is that of a man limping: he walks by his ordinary locomotive power, but limps inasmuch as he accidentally happens to be lame. The race does not limp. There is therefore no one primary and essential principle of all evil: but the first principle of all is one primary good, among the effects of which there ensues evil incidentally.

Hence it is said: I am the Lord, and there is none other, forming light and creating darkness, making peace and creating evil: I am the Lord doing all these things (Isa. xlv, 6, 7). And, Good things and evil things, life and death, poverty and rank are from God (Ecclus xi, 14). And, Against evil is good, and against life death; so against the just man is the sinner. And so behold all the works of the Most High, two and two, and one against one (Ecclus xxxiii, 15).

God is said to make and create evil things, inasmuch as He creates things that are good in themselves and yet hurtful to others: thus the wolf, though a good thing naturally in his kind, is evil to the sheep. Hence it is said: Shall there be evil in the city that the Lord hath not done? (Amos iii, 6.)

Hereby is excluded the error of those who suppose two primitive contrary principles, good and evil. This error of the early philosophers some evil-minded men have presumed to introduce into Christian teaching, the first of whom was Marcion, and afterwards the Manicheans, who have done most to spread this error.