Socrates thought that virtue and knowledge coincide; Kant, in his Religion, says:
Man (even the most wicked) does not, under any maxim whatsoever, repudiate the moral law in the manner of a rebel (renouncing obedience to it). ... We are not, then, to call the depravity of human nature wickedness [] to adopt evil as evil into our maxim as our incentives (for that is diabolical)...
So would an all-knowing being be able to will so much evil? Per the above, no. But is it logically possible to imagine being subjected to evil forever? I suppose I can "visualize" it, like I can visualize myself (as I often do) submerged in a lake of fire, and I can stipulate, "And it goes on forever..." and that "forever" doesn't seem to logically contradict anything per se, does it? So to say:
- X created the world.
- X created the world to torment it.
Again, (2) doesn't seem "self-contradictory" compared to (1) (assuming that creating-a-world is a meaningful enough notion, of course), unless we think that having the power to create worlds requires a certain moral disposition beforehand. For example, if in an old way of thinking there is something "intrinsically good" about existence in general, then the will-to-create must participate in this intrinsic goodness, or so an evil being will not have the power of such creation.F So though, "An evil being created the world," is not "directly self-contradictory," it is indirectly self-defeating, in a sense.
Perhaps that is far as this philosophical therapy could take you (accepting the abstract possibility of the world being created for an evil reason, but concluding also that you have no way of making the concepts involved precise enough to know if this apparent possibility is more than just 'logical' or if it also metaphysical/epistemic, etc.).
FSuppose, towards a possible contradiction, that it was possible for there to be a Form of Evil, in a roughly Platonic sense. Now if evil-in-itself can't be "willed" (if no one can deliberately act under the description, "What I'm doing is evil in general, and that's why I'm doing it!"), then either a Form of Evil is an exception to this rule, or conforms also hereto. It's more interesting, in my eyes, to see where the latter option leads us. If even a Form of Evil can't will contrary to the Form of the Good per se nota, what can it will for? Perhaps not even directly its own victory.
But so we assume that there must not be a lone ultimate Form of Evil, and this is not even just in counterpoint to the Form of the Good being "first among equals." It is of the essence of evil to be in a state of conflict, of aggression, and so there would be, if there be any, multiple evil Forms, vying against each other in various ways. And that is something they could very well will: each imagining, in its hostility towards the others, that its hatred is good, for it is hatred of something gravely evil, "isn't it"?
While "ignoring" their own malice, then. But is that possible? Even the Forms of Evil participate in the Form of the Good, to be Forms at all. And so they are caught up in the manner of the Form's influence on the possibility of knowledge (e.g. as by the power of the Forms of Knowledge and Power). How could a Form of Evil "not know" that it was doing something wrong by trying to destroy other Forms of Evil? Or by doing anything at all? If there are Forms of Good and Evil, then do the Evil ones not project their essence into the world of exemplars, through (or not through) a demiurge, but are "stationary" instead?