This region is the ideal cause of evil (as it were) as well as of good:  but, properly speaking, the formal character of evil has no efficient cause, for it consists in privation, as we shall see, namely, in that which the efficient cause does not bring about.  That is why the Schoolmen are wont to call the cause of evil deficient.

21.  Evil may be taken metaphysically, physically and morally. Metaphysical evil consists in mere imperfection, physical evil in suffering, and moral evil in sin.  Now although physical evil and moral evil be not necessary, it is enough that by virtue of the eternal verities they be possible.  And as this vast Region of Verities contains all possibilities it is necessary that there be an infinitude of possible worlds, that evil enter into divers of them, and that even the best of all contain a measure thereof.  Thus has God been induced to permit evil.

22.  But someone will say to me:  why speak you to us of ‘permitting’?  Is it not God that doeth the evil and that willeth it?  Here it will be necessary to explain what ‘permission’ is, so that it may be seen how this term is not employed without reason.  But before that one must explain the nature of will, which has its own degrees.  Taking it in the general sense, one may say that will consists in the inclination to do something in proportion to the good it contains.  This will is called antecedent when it is detached, and considers each good separately in the capacity of a good.  In this sense it may be said that God tends to all good, as good, ad perfectionem simpliciter simplicem, to speak like the Schoolmen, and that by an antecedent will.  He is earnestly disposed to sanctify and to save all men, to exclude sin, and to prevent damnation.  It may even be said that this will is efficacious of itself (per se), that is, in such sort that the effect would ensue if there were not some stronger reason to prevent it:  for this will does not pass into final exercise (ad summum conatum), else it would never fail to produce its full effect, God being the [137] master of all things.  Success entire and infallible belongs only to the consequent will, as it is called.  This it is which is complete; and in regard to it this rule obtains, that one never fails to do what one wills, when one has the power.  Now this consequent will, final and decisive, results from the conflict of all the antecedent wills, of those which tend towards good, even as of those which repel evil; and from the concurrence of all these particular wills comes the total will.  So in mechanics compound movement results from all the tendencies that concur in one and the same moving body, and satisfies each one equally, in so far as it is possible to do all at one time.  It is as if the moving body took equal account of these tendencies, as I once showed in one of the Paris Journals (7 Sept. 1693), when giving the general law of the compositions of movement.  In this sense also it may be said that the antecedent will is efficacious in a sense and even effective with success.