Commentaria in Summam contra Gentiles, Liber III

After St. Thomas has shown that evil is in things outside the intention, he now wishes to show that no essence is evil in itself ¹, taking evil formally, namely, for the very privation of a perfection due to be present. Concerning this he does two things: first, he shows what was proposed; second, he raises certain doubts and resolves them, in the two following chapters. I. It is argued therefore first as follows. Evil is a privation. Therefore it is not any essence in things. — The antecedent is clear from the use of the name. — But the consequence is proved. Because privation is not an essence, but a negation in a substance, that is, in a subject. Secondly. Each thing is good according to the fact that it has an essence. Therefore, since good and evil are opposed, nothing is evil according to the fact that it has an essence. Therefore etc. — The antecedent is proved. Because each thing has being according to its essence. But insofar as it has being, it has some good: since all things desire being. Note regarding that proposition, Each thing has being according to its essence, that this can be understood in two ways. In one way, that the very essence of the thing is its being. And in this way the proposition is false, nor does St. Thomas understand it thus: for in God alone is it true that his essence is his being, as was shown in the preceding sections ². — In another way, that the being of the thing proceeds from the very essence of the thing. And in this way the proposition is true, and is intended here. For a created simple essence is the formal cause of its being, and receptive of it. But a composite essence from matter and form is the proper receptive subject of being, so that, once the essence is constituted, the being of the supposit immediately results: and thus a thing is said to have being according to essence. The essence of a composite thing is also the formal cause of being by reason of its form, which gives being formally. II. Thirdly. Evil is neither an agent nor a thing made: since everything that acts, acts insofar as it is in act and perfect; and the terminus of any generation is form and good. Therefore evil is not any thing. — The consequence is clear: because every thing is either an agent or made. Fourthly. Every agent by acting intends good. Therefore no being insofar as it is of this kind, is evil. — The antecedent is proved. Because nothing tends to its contrary, but to what is similar and suitable. Note that, although this argument directly concludes that no made being is evil, nevertheless from this it is left universally that evil is no being. For if it is not any made being, much less will it be a being capable of making other things. III. Fifthly. What is evil in itself cannot be natural to anything. Therefore no essence is evil in itself. — The antecedent is proved. Because evil is the privation of that which is natural, as is clear from the definition of evil: for the substance of anything is the very nature of the thing; but an accident is caused by the principles of some substance.

2. Concerning this proposition, Everything that belongs to the genus of accident must be caused by the principles of some substance, and be natural to it, it is doubted. First, because thus every accident will be proper, and none will be common. For every accident is proper to that nature to which it is natural, and by whose principles it is caused.

Secondly, because grace and charity are accidents of the soul. And yet they are caused by the principles of no subject, and are natural to no subject.

3. For the clarification of this, it must be considered that, since every accident has to be defined through substance, on account of the natural dependence of an accident on a subject, as is stated in Quodlibet IX, a. 5 ³, ad 1; and, as is stated in the Treatise on Being and Essence ⁴, differences in accidents are taken from the diversity of the principles by which they are caused: it is necessary to say that every accident is caused by the principles of some substance, although frequently those principles are unknown to us. It is not necessary, however, that all be caused by the proper principles of some specific nature: but it suffices that they be caused either by the principles of the genus, or of the species, or even of the individual, as is gathered from the same Treatise on Being and Essence ⁵: for some accidents are proper to the genus, some to the species, and some indeed to the individual. But nevertheless it must be noted, from the same Treatise ⁶, and from II Sent., d. xxvi, a. 2, ad 2, that some accidents are caused by the principles of the subject with respect to complete act, as heat by fire; but some are caused with respect to aptitude only, as transparency is caused by the principles of air, yet is completed by something illuminating extrinsically; for the transparent in act includes light, which belongs to air from within only with respect to aptitude and habititude for the complement of act. — That therefore which is said here, that every accident is caused by the principles of some substance and is natural to it, is understood either with respect to complete act, or with respect to aptitude.

4. To the first in the opposite, therefore, it is answered that certainly every accident is proper with respect to some subject, either generic or specific or singular, with respect to this, that it is caused by the principles of the subject, in the manner explained; and is compared to it as proper act is compared to proper potency; and also with respect to this, that it is sustained through the subject. For although there are certain accidents, as is said in I Sent., d. xvii, q. 1, a. 2, ad 2, which are repugnant to the principles of the subject and are introduced by violence, as is the case with heat introduced into water; nevertheless they must, either with respect to complete act or with respect to aptitude and habititude, determine for themselves some subject, according to genus or species or individual, without which they cannot be with respect to either of them. For although heat can be in something according to act through violence, nevertheless it is not in it according to aptitude and habititude.

Speaking in this sense, no accident is common. But that accident is divided into proper and common, this division is taken by comparison to the most specific species. For something belongs to one most specific species, as risibility to man: but something belongs to several species, as whiteness to snow, milk, the swan, and others.

5. To the second it is said, from II Sent., in the place previously cited, that although grace and charity are not caused by the principles of the subject with respect to complete act, yet the receptivity of these always follows the subject, and is caused by the principles of the subject, and thus can be called natural, as is clear in that which is to be susceptible of instruction.

It could also be said that St. Thomas is speaking about accidents which can be caused by a natural agent. But grace and charity are not such accidents.

IV. Sixthly. Every essence is either a form, or having a form: since each thing is placed in a genus or species through form. Therefore it is good. For form, insofar as it is of this kind, has the ratio of goodness: both because it is the principle of action, and the end intended by the agent; and because it is the act by which each thing is perfect. Therefore etc.

Seventhly. Act, insofar as it is of this kind, is good: since each thing, according as it is in act, is perfect. Potency also is something good: since it tends to act; and is proportionate to act, but not contrary; and is in the same genus with it; but privation does not belong to it except per accidens, namely insofar as it is joined to form. Therefore every being, insofar as it is being, is good. — The consequence is clear. Because being is divided through act and potency.

Eighthly. Evil cannot be an effect of God. Therefore, etc. — The consequence is proved. Because all being, in whatever way it is, is from God, as was shown in the Second of this work. — The antecedent is also proved. Because evil cannot be an effect of good, namely per se. But God is the very essence of goodness.

The conclusion is confirmed by the authority of Gen. I; and Eccles. III; and I Tim. IV; and of Dionysius, IV ch. of Div.

The error of the Manicheans, who posit that some things are evil according to their natures, is also excluded.