Atheist computer scientist Jeffrey Shallit and I have been having a discussion about the nature of our abstract thoughts. Are they material things in our brain, or are they immaterial?

Shallit thinks they are material:

[Abstract thoughts are] patterns in brains, of course. If you weren’t so stuck in medieval philosophy, even you could have figured that one out… [p]attern is the differential arrangement of matter…

Shallit is right about some kinds of thoughts, and wrong about others. We have two kinds of thoughts, understood most broadly: thoughts about particulars, and thoughts about universals.

Thoughts about particulars are perceptions and related acts, such as apprehension, imagination, memory of particulars, among other acts. Classically these are called interior senses.

Thoughts about universals are abstractions (also called concepts) and related acts including intellective will. Classically these are called rational faculties.

Perceptions and abstractions have different objects. Perceptions are material and abstractions are immaterial, just as the objects of perceptions are material (particulars) and the objects of abstractions are immaterial (universals).

An example will help make it more clear.

Imagine that I am sitting at my desk looking at my dog Pipa. Pipa is a Bichon Frise, and she likes to sit by my desk because I give her treats and I play tug with her toys. Pipa is a particular — she weighs 15 pounds, is fluffy and white. When I perceive Pipa, I’m thinking of a particular. The light bouncing off her stimulates my retina cells, which stimulate my visual tract cells in my brain, which stimulate my visual association cells and ultimately cause me to perceive Pipa.

Exactly how this happens isn’t completely worked out yet, but there is no doubt that it is a material process. It will be necessary to have a deeper understanding of what matter is, of course, because our modern understanding of matter precludes subjective experience, but my perception of Pipa is material in some sense of matter. There is no reason to invoke immaterial powers in order to explain my perception of my little dog. My perception of Pipa is a brain state of some sort — a particular configuration of a neuron, or whatever. A pattern, as Shallit would say.

Now imagine that I am sitting at my desk contemplating justice. When I contemplate justice, I contemplate an abstraction — a universal. Justice doesn’t have a weight or texture or color. It’s abstract, not any particular object in my environment. Unlike Pipa, justice doesn’t stimulate my retinal cells. Justice doesn’t bark or have fluff or smell like doggy, so neither does it stimulate my cochlear cells, or my touch receptors, or my olfactory cells. Justice doesn’t stimulate my senses at all. I contemplate it as an abstraction. I don’t perceive it as a particular.

Here’s the important question: can contemplation of justice be a brain state for me, like perception of Pipa is a brain state? No, it can’t.

This is why. Imagine that justice is a brain state — a particular configuration of a neuron, say. Because a configured neuron (or any brain state) is a particular, my concept of justice, which is a universal, cannot be instantiated in it. That is, my concept of justice can’t actually be a configured neuron, in the same way that my perception of Pipa can be a configured neuron.

Now it is altogether possible for justice to be represented in a configured neuron, just as justice is represented in the electrons on the computer screen you are reading. But representation is not the same thing as instantiation. In order for justice to be represented in my brain, there must be some way in which “justice” is linked to “configured neuron”, like a map or a code in my brain. But any map that links the concept of justice to my configured neuron must presuppose the concept of justice. I can’t map my concept to my configured neuron unless I already have my concept.

The representation of a concept presupposes the concept, and thus a brain state can’t be my concept of justice. A concept is prior to, and irreducible to, any state of matter.

Notice that this is not a problem for my perception of a particular. If I accept a definition of matter than admits subjectivity (e.g. hylemorphism), my perception of my dog Pipa can be a configured neuron.

Perception of a particular can be a brain state. Contemplation of a universal cannot be a brain state.

Thoughts based on sense — vision, hearing, smell, touch, taste — are material. Thoughts of abstractions are immaterial.

It should be noted that our objects of thought are characteristically a cacophony of particulars and universals — a dog and justice and a desk and world peace — and that contemplation of universals is often closely associated with perception of particulars — when I think of justice, I may also have an image of the Supreme Court building in my mind. Contemplation of universals is accompanied by perception of particulars in ordinary thought. Immaterial and material mental powers work in concert.

But contemplation in itself is an immaterial power, and materialism is an inadequate predicate to fully explain the human mind.

Image credit: Arashkashani (Own work) [Public domain], via Wikimedia Commons.