This week we’re dealing with Aquinas on Plato’s realm of Forms. We’ve been touching on related topics recently, and in 1a.84.4, Aquinas finally gets around to explaining his theory of knowledge and why he reckons Plato’s not got it right. This article also serves as a great little overview of the core differences between Plato and Aristotle, at least in this regard. I read somewhere that Aquinas is sometimes criticised for not saying anything original – the counter-argument, apparently, is that he might not have said anything original, but his work is laid out in a really clear way. That clarity is certainly at the fore in this article.

So 1a.84 in general is asking how souls know things while still attached to bodies. In 84.1, Aquinas argues that the soul knows things through the intellect, which seems obvious but okay. In 84.2 and 3 Aquinas is arguing that humans don’t know in the same way that God or angels know. And in 84.4, Aquinas comes to Plato. He asks “Do species come to the soul through the influence of subsistent immaterial forms?” We’re going to skip ahead to the response here, because it lays out Plato’s position and what Aquinas actually wants to say about it. I’ll paraphrase it here, and if I get anything wrong, it’s Aquinas’s fault.

So the basic idea of Plato’s realm of Forms is that there’s one true Form for each type of thing, and all the actual instances of that thing in the real world derive from the one Form. So there’s heaps of cats in the world, right, and they’re all instances of the one true Cat Form. Our physical reality can engage with those Forms in two ways: first, all material things participate in the Form that they’re derived from, and second, our brains understand things by engaging (or ‘participating’) in the Form. So the Form gives shape to matter, and our brains get images of Forms and that’s how we understand things.

But Aquinas pulls out his little sassy pants, and says that “if this position were true, we would not need the senses in order to understand.” If you can get knowledge by participating intellectually in the abstract Forms, why do you need eyeballs? More to the point, even if you don’t have eyeballs, you should still know about colour and brightness and so on – not by external reports from your friends, but internally by participating in the Forms of colour and brightness. Making the point explicitly, Aquinas writes that “in this view, no satisfactory reason can be given why our soul is united to the body.” There’s no need for the soul to have a body, because under this logic, bodies just weigh us down, making us understand things through the dark mirror of physical reality. We’d really all just be better off dead, under that logic, and also it seems pointless for God to make us go through all this nonsense of embodiment.

It all just seems a little silly to Aquinas, so he chucks out Plato and his Forms, and turns to Aristotle. This is 1a.84.6 – “Aristotle proves that the beginning of our knowledge is in the senses.” He actually goes back over a point he raised earlier on the relationship between body and soul (1a.75.1). Basically, if your soul is purely spiritual, and your body is purely physical, how do they interface with each other? What’s the point of connection between two things that don’t exist on similar planes? Aquinas’s own solution is that the soul is the form of the body. However here he’s arguing that Plato is confronted by the same problem – if the soul is participating in abstract Forms for its knowledge, how does sensory information (which comes in through the body) cause the soul (which is spiritual) to start participating in these Forms? It’s the same basic question – how does corporeal data turn into this abstracted Form-knowledge? What’s the interface? Aquinas summarises Plato’s position thus: “intellectual knowledge does not start from sensible knowledge, nor does sensible knowledge itself proceed totally from sensible things. Rather, sensible objects awaken the sensible soul to sense, and, similarly, the senses awaken the intellectual soul to understand.” 

Aquinas himself ends up following Aristotle’s opinion on the topic, which frankly is just much more sensible. Basically, understanding belongs to the body-soul composite, which, you know, obviously. Even if you’re not big on the whole ‘soul’ idea, it’s pretty clear that understanding is a joint effort between the senses and the mind. You get data in, and then your brain makes meaning from the data. Or as Aquinas puts it, “intellectual activity is caused by the senses by way of these images.” 

Aquinas actually spends a fair bit of time positioning himself here against and within several different traditions. He’s balancing Aristotle against Plato and Democritus in trying to lay out his own position. I’ve skipped over most of it, because I think the more basic point for laypeople like me is simply that for Aquinas, knowledge comes through the body-soul composite. You receive an image, and you process it. As an example of part of that hedging, Aquinas clarifies that the image itself isn’t the sole cause of knowledge. Imagine, uh, a situation where you see something, and that thing essentially invades your brain and causes a bunch of changes – the image itself actually does the work of creating knowledge. That seems nuts – and Aquinas takes the time to position himself against that idea. Rather, he says, you have to think about the images that you receive. “It is not right to say that sensible knowledge is the total and complete cause of intellectual knowledge – better to say it is somehow the material of the cause.” The data alone isn’t enough – you also have to process it with yo brainpan.