Aquinas: Does God Know Sin?

We’ve got some fun coming up now – we’re about to get into God’s will, which includes discussions of whether or not God wills evil, or whether or not God wills people to go to hell. Predestination, kiddies, it’s coming. As an entrée, we’ll look at God’s knowledge. Does God know evil? If He does, then evil has its roots in God – “for God’s knowledge stands to all created things as the artist’s to his products,” according to Aquinas (1a.14.8). If He doesn’t, then… God doesn’t know everything? This is one of the things I love about Aquinas – he sets up a framework of how something works, and then goes ‘Right, how can I break this?’

So we’re looking at 1a.14.10, where Aquinas asks whether God knows evil. He’s got a couple arguments that we’re not really going to touch on, because they draw on stuff we haven’t talked about, and I like to be relatively self-contained here. So for example he argues that “all knowledge is either the cause of what is known or caused by it” – so that’s a reference back to 14.8, quoted above, where Aquinas argues that God’s knowledge is actually the cause of things. He draws a little bit on Augustine in that article, who says that things exist because God knows them. That’s sort of the foundation for the pickle he’s getting into now – if that argument holds, is God’s knowledge the cause of evil?

We’ve talked previously about how Augustine sees evil as a lack of goodness – so that it’s not a quote-unquote thing, but it’s a lack of something. So we can use the metaphor of light and darkness – light is a thing, a wave/particle, and darkness is what happens when that thing isn’t present. Aquinas sort of runs the same line – I thought we’d talked about that before too, but flicking back through what I’ve published on Aquinas, apparently not. Ah well – anyway, Aquinas runs the same line as Augustine on the whole sin-as-lack thing. This actually ends up forming one prong of his argument for God not knowing evil – if God’s perfect, then He doesn’t have any sin in Him, right? He lacks nothing, He’s got every good quality within Himself. But Aquinas has already previously argued that “in God, to be and to know are the same”, which… ugh. Okay, we’re gonna have to deal with this briefly.

So Aquinas firstly argues that God knows Himself (14.1-3), which seems like a sort of ‘duh’ argument, but there you go. He then argues that in God, the act of being and the act of knowledge are the same (14.4). I don’t really understand it, but you can go read it for yourself. Aquinas proceeds to suggest that God can’t know anything aside from Himself, because if He does, then He’s sort of completed or made more perfect by that knowledge (14.5). The idea is that knowledge and understanding make you quote-unquote ‘more perfect’, and if God is receiving new knowledge from things outside of Himself, then He’s being made more perfect, which should be impossible because God’s already perfect. So He can’t know anything outside of Himself.

So then how does He know us? The answer is that He knows us through Himself. To the extent that we are perfect, the argument goes, we are likenesses of God – which is fair enough. Every good thing that we have or are is already in God, so it makes sense that He knows us as sort of instances of qualities He already has in Himself. There’s some other arguments along the way – does God know each of us specifically as individuals, or does He just know us in a general sort of sense (14.6)? If He knows things through Himself, can He know hypothetical or non-existent things? How can we say that non-existent things have any sort of ‘existence’ in God (14.9)? That one’s pretty fun: “God’s knowledge is the cause of the things He knows. But it is not the cause of non-existent things, since they have no cause [because they don’t exist, right]. Therefore God has no knowledge of non-existent things.”

So part of this whole ‘God knowing us through Himself’ thing is the idea that in God knowledge and being are the same. But God doesn’t have any privation in Himself, because He’s perfect. So if He knows everything through its likeness to Himself, how can He know sin, which has no sort of primary existence within Him? This is the same sort of argument as in 14.9: if 14.9 asks ‘How can things that don’t exist be said to exist in God?’, 14.10 asks ‘How can things that don’t exist in God (sin) be said to exist in God?’. Remember: according to Aquinas, existence and knowledge are the same in God. God only knows things through Himself – so if sin doesn’t exist in God (which it doesn’t), He can’t know it.

The response, then, is that God sort of knows evil through good. He doesn’t know evil directly, per se, but He knows what good looks like when there’s different amounts of it. So He knows what perfect goodness looks like, and He knows what perfect goodness looks like when you take bits away from it. He doesn’t know evil directly, but when you think about it you can’t really know evil directly, because evil’s not actually a thing: “evil is not knowable through itself, because evil of its very nature is the privation of good. And thus it cannot be defined or known except through good.” We can jump back to our light metaphor – it doesn’t make sense to measure darkness in terms of how many dark particles are there. Dark’s not a thing – light is a thing, and we can talk about there being differing amounts of light, but dark’s not actually a thing. It’s just a lack. So no, evil isn’t in God, but yes, God sort of knows evil indirectly – or rather, He knows what it looks like when good is only there to a certain degree. Which really is all evil is anyway.


  1. This may be a dumb question after reading, Does God know evil, but when it’s said that we then gained knowledge of good and evil, does that mean that we began to look at evil, not through goodness as a privation of it as God does, but as a thing that has existence though evil doesn’t really exist in and of itself? Is this what makes us broken, since we perceive evil to exist when it doesn’t in its truest sense?


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