  Regarding the procession of creatures from God, Willliam is concerned to attack a range of errors. In On the Universe 1.1 he attacks the error of the Manichees. Though he refers to Mani, the third-century originator of the Manichee sect, he seems chiefly concerned with the Cathars of his day. The Manichees deny God is the ultimate source of all things and instead posit two first principles, one good and one evil. Only in this way, they think, can we explain the presence of both good and evil in the world. William thinks a fundamental motivation for this view is the principle that “from one of two contraries the other cannot come of itself” (OO I, 602a; Teske 1998a, 54), and hence that evil cannot come from good but must stem from its own first principle. He replies that although one contrary cannot of itself (per se) be from the other, it is perfectly possible for it to be from the other incidentally (per accidens), and he gives everyday examples to illustrate. Thus, “drunkenness comes from wine. In that case it is evident that an evil comes from a good, unless one would say that wine is not good” (OO I, 602a; Teske 1998a, 54). Likewise, there is a sense in which evil is ultimately from God, though incidentally and not as something God aims at or intends as such. The evil of sin, for example, is a consequence of God's creating creatures with free will and permitting their misuse of it.