In The Immortal Mind, coauthored with Denyse O’Leary, we detail both neuroscientific and logical reasons why human abstract thought — the intellect — is an immaterial, spiritual power of the human soul. Consider as an example our ability to think about “perfect” concepts.

In Search of the Perfect Triangle

There are two ways we can think of a triangle. One way is to form a mental image, likely based on a triangle we have seen on a piece of paper. We may imagine a triangle drawn in blue ink, sort-of flat, with kind-of straight sides, and internal angles that add to 180 degrees, more or less.

The other way is to conceive abstractly of what a triangle is: it is a closed plane figure with three straight sides whose interior angles sum to 180 degrees. Note that this abstract idea of a triangle differs fundamentally from the image of a triangle that we may see in our mind or on a piece of paper: the abstract concept of a triangle is perfect, whereas the image of a triangle is always imperfect in one way or another. 

How Is It Possible to Conceive of a Perfect Thing?

From the materialist perspective, every mental state is a brain state, and no brain state — no physical state — can ever be perfect. Nothing physical can be exact, with the absolute limit of exactitude given by Heisenberg’s Uncertainty Principle. No physical line is perfectly straight. No physical circle is perfectly circular. No angle is exactly 180 degrees.

Yet our intellects can grasp perfection — an exact triangle, which can never exist in physical reality. So the challenge to the materialist theory that every mental state is a brain state is: how can a perfect thought be an imperfect brain state?

The ability of abstract thought to entertain the idea of perfection precludes its generation from imperfect matter. This proof of the immateriality of the human intellect is classical; it dates back to Aristotle (384–322 BC). It is, in my view, quite convincing, because it points out that material brain processes belong to a different category of being than abstract thought. Abstract thought cannot in principle arise wholly from brain processes.

Rather, we are embodied spiritual creatures and abstract thought is a power of our spiritual soul. As we point out in The Immortal Mind, neuroscience points to this truth about us, and logic points to it as well.

Cross-posted at Mind Matters News.