Celsus in the next place, as if he were able to tell certain secrets regarding the origin of evils, but chose rather to keep silence, and say only what was suitable to the multitude, continues as follows: “It is sufficient to say to the multitude regarding the origin of evils, that they do not proceed from God, but cleave to matter, and dwell among mortal things.” It is true, certainly, that evils do not proceed from God; for according to Jeremiah, one of our prophets, it is certain that “out of the mouth of the Most High proceeds not evil and good.” But to maintain that matter, dwelling among mortal things, is the cause of evils, is in our opinion not true. For it is the mind of each individual which is the cause of the evil which arises in him, and this is evil (in the abstract); while the actions which proceed from it are wicked, and there is, to speak with accuracy, nothing else in our view that is evil. I am aware, however, that this topic requires very elaborate treatment, which (by the grace of God enlightening the mind) may be successfully attempted by him who is deemed by God worthy to attain the necessary knowledge on this subject.
Source: Against Celsus (New Advent)