Concerning the Nature of Good, Against the Manichaeans

But it may happen, that a certain nature which has been ranked as more excellent by reason of natural measure and form, though corrupt, is even yet better than another incorrupt which has been ranked lower by reason of an inferior natural measure and form: as in the estimation of men, according to the quality which presents itself to view, corrupt gold is assuredly better than incorrupt silver, and corrupt silver than incorrupt lead; so also in more powerful spiritual natures a rational spirit even corrupted through an evil will is better than an irrational though incorrupt, and better is any spirit whatever even corrupt than any body whatever though incorrupt. For better is a nature which, when it is present in a body, furnishes it with life, than that to which life is furnished. But however corrupt may be the spirit of life that has been made, it can furnish life to a body, and hence, though corrupt, it is better than the body though incorrupt.