This post is about an incidental finding in my PhD research. I can't fit it into my dissertation, but it's a fascinating bit of wisdom everyone should know about.

The goal of my dissertation is to explain and defend free will as Orthodox Christianity understands it. At the same time, I'm working to kill the determinist hype in neuroscience.

If you have a lot of questions after reading that, good!

It's a complicated project and has to be written in PhD language.

Once I finish, I intend to publish my discoveries on The Orthodox Snake, but in a way that is fun, readable, & creative. It’ll be a while.

I've been reading the Latin Catholic Scholastics lately. I recently discovered Saint Thomas Aquinas knew some basic neuroscience about:

Aquinas classified these processes together & called them the "Common Sense." He knew these "Common Sense" powers come from the brain. He even correctly guessed which part of the brain is responsible for it.

Aquinas had a rough neuroscience theory 700 years before neuroscience even had names for these brain functions. In order to appreciate his insights on the brain, let’s check out his insights on sensation.

Aquinas classified senses as either "external" or "internal." He counted 5 external senses & 4 internal senses. You'll be familiar with the external senses - they are the 5 senses taught in school.

The external senses...

The internal senses...

You've doubtless heard about Imagination, Memory, Cognition & Common Sense. But you probably find it strange to group them together & call them senses. Why do that?

The short answer is Aquinas wanted to be clear about which powers depend on a physical organ & which do not.

If Aquinas calls some function a sense, he thinks it depends on a bodily organ. Aquinas knew almost all human powers depend on an organ.

Most of our mental abilities depend on the brain. Memory, Imagination, Proprioception, Cognition, & Apprehension all rely on it. And the brain is formed by genetics, environment & habit.

Orthodox Christians are fortunate Aquinas suspected as much because neuroscience & psychology are exhaustively demonstrating so now.

Should Christians be scandalized that much of our conscious experience depends on the brain?

No, we shouldn't, because we should know that our conscious ego is not our immaterial spirit.

Materialism, introduced by the Enlightenment, threatens the existence of immortal human spirits. To reassure ourselves we have a spirit, Westerners now believe our ego is our spirit. But that is incorrect.

Opinions on the soul changed because secular culture changed, not because of any Church Council. Yet, some Christians accept the new secular opinion as a philosophical fact.

Most now assume every conscious action comes from our immaterial spirit. So then, when neuroscience discovers physical mechanisms powering memory, imagination, emotion, or whatever, people feel the discovery threatens belief in a spiritual afterlife.

And many of those people are Christians, although they should know better. The truth is, we conflated our brain with our immaterial spirit & confused ourselves about both.

Then again, the problem isn’t “Christians are stupid!” New Atheists have been claiming every famous neuroscience discovery in the past 40 years is "scientific proof there is no spirit!"

So I can't blame the laity for worrying about what intellectuals keep telling them.

We should now understand that Common Sense is a brain process, and we should feel comfortable about that. Let's now let's hear what Aquinas had to say about it.

Common Sense is the internal sense that receives signals from the external sensory organs, in order to:

Neuroscience now has technical terms for each of those processes. If we use modern terms, we can say the Common Sense is responsible for the operations of:

Lo & behold, modern neuroscientists and Saint Thomas Aquinas all agree: these three operations depend on the brain.

Modern language is less precise than Scholastic language on "Common Sense." We still hear the term "Common Sense," but it doesn't mean what it meant to Aquinas.

Today we define "Common Sense" as "the universal moral principles known by everyone." It's a weird idea, & if you think about it, it doesn't make much sense.

Today "Common Sense" is usually a buzzword in political slogans. Aquinas had something different in mind.

As Aquinas understood it, Common Sense doesn't deal with morality. The immaterial Intellect is what deals with moral principles & judgements. Common Sense helps us handle physical concerns. So the proper study of Common Sense belongs to neuroscience, not ethics.

Like every Orthodox Christian, Aquinas professed the human soul has an immaterial aspect. We want to call that "spirit," but Aquinas called it "Intellect."

The immaterial Intellect has critical functions in human life, but it can't do everything. It doesn't imagine - imagination is an internal sense. It can't remember any particular thing - that's what memory does, and memory depends on the brain.

The Intellect creates concepts, makes judgements, and reasons.

The Will is an aspect of the Intellect too! The technical term Aquinas uses for the Will is the "Appetitive Intellect." His point is that the Will is just the Intellect with an Appetite (for something Good, True, and/or Beautiful).

According to Aquinas, the Intellect (including the Will!) are the aspects that survive death. The Intellect is the immaterial aspect of the human soul.

I say "aspect" rather than "part" because the Intellect & the Body aren't two foreign objects slammed together. In Orthodox Christianity, they exist harmoniously in one human soul.

The Intellect is pretty important. But it's not responsible for most of the processes powering our daily experiences. Humans sense, react, remember, imagine, act on habit, feel urges.

Most of our conscious concerns relate to our physical experiences. So should it really surprise us that humans have a sophisticated bodily organ to help us deal with those concerns?

Aquinas suspected all the internal senses (imagination, memory, cognition, & Common Sense) are powered by a...

That's the original Latin. There are a few different ways to translate it:

Ventricles are cavities that pump cerebrospinal fluid throughout the brain. Modern anatomy gave a new name to the Middle Ventricle.

It's now the Third Ventricle (because the First & Second begin in front & they're side-by-side). A critical function, but Ventricles don't contain any neurons.

So it sounds obviously wrong to attribute brain functions to the Middle Third Ventricle, but his neuroscience isn't totally absurd.

The ventricles act as landmarks in dissection, & dissection was the only way to examine the brain in Medieval times. Aquinas is using the only landmark available.

If we read Aquinas charitably, he draws our attention to the brain regions around the Third Ventricle. Those regions are now known as the Diencephalon.

The Diencephalon is a group of brain regions around the Third Ventricle. It's involved in just about every process performed by the human body, from hormones to motor action. It might be processing signals every moment of your life.

The largest region in the Diencephalon group is the Thalamus. I'm turning your attention to the Thalamus because there’s good evidence it performs the 3 functions Aquinas called Common Sense.

A disclaimer: no brain region is limited to a few simple functions. There are undoubtedly other functions of the Thalamus, & most of them are probably still unknown.

There's more to discover in the Thalamus, but there's already solid evidence that it powers Common Sense. It works to unify experience, recognize objects, & orient the body.

That means Aquinas was correct that Common Sense is powered by [the regions around] the Middle [Third] Ventricle.

Neuroscientists today know far more about the brain than anyone did in Medieval times. That's undeniable. The point of this post isn't to encourage anyone to reject Modernity; embrace thatched roof.

My point is that Medieval scholastics weren't the Dark Age morons we've been taught to believe. Take Aquinas: he's so insightful that he got some neuroscience correct... before neuroscience existed.

And if he had some good ideas for a field that wouldn't exist for another 600 years, imagine how insightful he must be in an established field, like theology, philosophy, ethics, and so on.

His explanation certainly isn't exhaustive, nor precise. Aquinas theorized the Diencephalon powers every mental process, not just Common Sense. His theory is about as precise as a sawed-off shotgun.

Say any brain region does everything. If, in reality, it does anything at all, you're still partially correct. While the Diencephalon has essential functions, it isn't solely responsible for everything.

Errors & all, it's still incredible that 700 years ago, a Saint-Theologian knew the basics about Multisensory Integration, Object Recognition, & Proprioception.

He knew these were necessary brain functions before we had distinct names for them. He correctly, although imprecisely, concluded that Common Sense depends on the area around the Middle Third Ventricle.

The achievement is more impressive when you know the dark episodes of modern psychology. Psychology has had its own dark ages, all of them centuries after Aquinas. All of them with errors greater than Aquinas' theory.

For example, Phrenology was popular throughout the 1700s & 1800s. Phrenology theorized that skull shape indicates intelligence, personality, & moral character. Practicing psychologists made careers off writing personality inventories based on skull dimples.

Aquinas sounds positively enlightened compared to reading a skull like a crystal ball, which is the more recent practice. But according to history as told by the Enlightenment, Aquinas was the lord of the Dark Age.

Supposedly, the West didn't find Enlightenment until we dumped Aquinas. But in this particular case, it seems we took a big step backward for a while.

Aquinas was a wise guy. Some of his neuroscience & psychology theories still retain their wisdom after centuries of scientific advances.