Creation and Evil

Ergo malum est, si praeter pertinaciam velitis attendere, deficere ab essentia et ad id tendere ut non sit. Quocirca cum in Catholica dicitur omnium naturarum atque substantiarum esse auctorem Deum, simul intelligitur ab eis qui haec possunt intelligere, non esse Deum auctorem mali. Qui enim potest ille, qui omnium quae sunt causa est ut sint, causa esse rursus, ut non sint id est, ut ab essentia deficiant et ad non esse tendant? Quod malum generale esse clamat verissima ratio. At vero illa vestra gens mali, quam vultis esse summum malum, quomodo erit contra naturam id est contra substantiam, cum eam naturam atque substantiam esse dicatis? Si enim contra se facit, ipsum esse sibi adimit; quod si perfecerit, tunc demum perveniet ad summum malum. Non autem perficiet, quia eam non modo esse verum etiam sempiternam esse vultis. Non potest igitur esse summum malum, quod perhibetur esse substantia. Sed quid faciam? Scio plures esse in vobis, qui haec intelligere omnino nequeant. Scio rursus esse quosdam, qui quamquam bono ingenio utcumque ista videant, mala tamen voluntate qua ipsum quoque ingenium sunt amissuri, pertinaciter agant et quaerant potius quid adversus ista dicant, quod tardis et imbecillis facile persuadeatur, quam vera esse consentiant. Non me tamen scripsisse poenitebit quod aut quisquam in vobis tandem non iniquo iudicio consideret vestrumque relinquat errorem, aut quod ingeniosi et Deo subditi atque adhuc ab studio vestro integri cum legerint, non possint vestris sermonibus decipi. Quaeramus ergo ista diligentius et quantum fieri potest, planius. Percunctor vos iterum quid sit malum. Si dixeritis id quod nocet, neque hic mentiemini. Sed quaeso animadvertite, quaeso vigilate, quaeso deponite studia partium, et verum non vincendi sed inveniendi gratia quaerite. Sanctus Augustinus Hipponensi, De Moribus Ecclesiae Catholicae Et De Moribus Manichaeorum Libri Duo, Liber Secundus

Therefore, if you are willing to attend to the matter without stubbornness, evil is that which declines from essence and tends to that which is not. Whence when the Catholic Church says that God is the creator of all natures and substances, at the same it is understood, by those who can understand this, that God is not the author of evil. For how can He who is the cause of all things that are at the same time be the cause of their not being, that is, of their falling from being and tending to nothing? For this is what reason plainly cries out evil to be. Now, your race of evil, which you make the supreme evil, how will it be against nature, that is, against substance, when you say it is a nature and substance? For if it is acting against itself, it is depriving itself of its own existence, and when that is completed, then it will come at last to be the supreme evil. But this cannot be, because you wish it not only to be, but to be everlasting. Thus that which is held to be a substance cannot be the chief evil. But what shall I do? I know that there are many among you who cannot understand any of this. I know, too, that there are some who, although they have a good understanding and can see these things, with a bad will which will ruin their understanding, act stubbornly and seek  to exert themselves to find what to say against this that they might persuade inactive and feeble minds, rather than assenting to the truth. However, I shall not regret having written either what one of you may come some day to consider without hostile judgement and be led to abandon your error, or what men of understanding and subject to God, and who are still untainted by your way, may read and so be kept from being deceived by your words. Let us then inquire more carefully, and, if possible, more openly. I ask you again to tell me what evil is. If you say it is that which is hurtful, here, too, you will not lie. But consider, I ask you, be on your guard, I beg, to lay aside party spirit, and seek truth not for the sake of victory but for the finding of it. Saint Augustine of Hippo, On the Morals of the Catholic Church and of the Morals of the Manichaeans, Book 2