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CHAPTER XII: THAT EVIL DOES NOT ENTIRELY DESTROY GOOD
IT is clear from the foregoing that however much evil be increased it can never destroy good entirely: since there must always remain the subject of evil, as long as evil remains. Now the subject of evil is a good. Therefore, some good must always remain. But seeing that evil may be increased indefinitely, and that good is always diminished by the increase of evil: it would seem that good is decreased by evil indefinitely. Now a good that can be diminished by evil must needs be finite: because infinite good is incompatible with evil, as we proved in the First Book. Seemingly, therefore, sometimes a good is wholly destroyed by evil: since if something is subtracted indefinitely from the finite, this must at length be destroyed through such subtraction.
Nor may it be said, as some say, that if the subsequent subtraction be made in the same proportion as the preceding one, and continue thus indefinitely, the good cannot be destroyed, as may be seen in the division of a continuous quantity. Thus if from a line two cubits long you subtract half, and from the remainder subtract half, and continue thus indefinitely, there will always remain something to be divided. But in this process of division that which is subtracted afterwards must always be less in quantity: for half of the whole which was subtracted at first, is greater in absolute quantity than half of the half, albeit the same proportion remains. This, however, nowise applies to the diminution of good by evil. Because the more a good is diminished by an evil, the weaker it becomes, and thus it will be more capable of diminution by the subsequent evil. Again this subsequent evil may be equal to or greater than the previous one: wherefore it will not happen that a smaller quantity of good will always be subsequently subtracted from the good, even if the same proportion be observed.
We must therefore find a different solution. It is clear from what has been already said, that evil entirely destroys the opposite good, as blindness destroys sight: yet there must needs remain the good which is the subject of that evil. And this subject, as such, has the aspect of a good, considered as in potentiality to the actuality of the good which is removed by the evil. Wherefore the less it is in potentiality to that good, the less good will it be. Now a subject becomes less in potentiality to a form, not indeed by the mere subtraction of some part of that subject; nor by the subtraction of some part of its potentiality; but by the fact that the potentiality is hindered by a contrary actuality from reaching to the actuality of the form: thus according as heat is the more increased in a subject, the less is that subject potentially cold. Wherefore good is diminished by evil more by the addition of its contrary, than by the subtraction of good. This applies also to what we have said of evil. For we have said that evil is incidental beside the intention of the agent, which always intends some good, the result of which is the exclusion of some other good opposed thereto. Hence the more we increase that intended good, the result of which is an evil beside the agent's intention, the more the potentiality to the contrary good will be diminished: and it is thus that the diminution of good by evil increases.
Now this diminution of good by evil cannot go on indefinitely in the physical order. Because all physical forms and forces are limited, and reach a certain term beyond which they cannot reach. Consequently neither can a contrary form, nor can the power of a contrary agent, be increased indefinitely, so as to result in the indefinite diminution of good by evil.
On the other hand this diminution can proceed indefinitely in moral matters. Because the intellect and will have no limit fixed to their actions: for the intellect can proceed indefinitely in understanding: wherefore the mathematical species of numbers and figures are infinite. In like manner the will goes on indefinitely in willing: since he who wills to commit a theft, can so will again, and so on to infinity. Now the more the will tends to undue ends, the more difficult is it for it to return to its proper and due end: as is evident in those who have acquired a vicious habit through sinning frequently. Hence the good of natural aptitude may be diminished indefinitely by moral evil; yet it will never be entirely destroyed, and will always accompany the nature that remains.
|Source: St. Thomas Aquinas, The Summa Contra Gentiles, trans. by The English Dominican Fathers from the latest Leonine Edition, Benzinger Brothers: New York, 1924.|