Your organs have jobs to do. Your heart pumps blood. Your lungs exchange oxygen and carbon dioxide. Your kidneys make urine. Your skin keeps you inside and your environment outside.
So what does your brain do? We naturally answer: "It makes me think, use my mind, stuff like that." But that's not exactly true. The brain does have a job, of course, but it's a more limited job than producing all that is in our mind. Neuroscience tells a very different story about what the brain does. And it's a fascinating one.
Neurosurgeon Wilder Penfield (1891‒1976), who pioneered epilepsy surgery at the Montreal Neurological Institute in the mid-20th century, asked this very question: What does the brain do? He explored the question during eleven hundred "awake" brain operations over four decades. He needed patients to be awake so that he could communicate with them, to be sure that he was not damaging vital tissue while removing the tissue that was prone to epileptic seizures.
Penfield could do brain surgery while a patient is awake because the brain has no pain sensors. A local anesthetic (similar to the novocaine used in dentists' offices) ensures that there is no pain in the scalp either during the surgery. Neurosurgeons still do this type of surgery today.
While epilepsy patients were awake and their responses to brain stimulation could be observed, he mapped their brains using electrical probes to find and remove seizure foci but also to determine which parts of the patients' brains did what. He could answer questions like "What part of the brain makes us move our muscles?", "What part of the brain enables us to see?" and "What part of the brain enables us to have memories and emotions?"
What fascinated Penfield is not so much what he found -- i.e., which parts of the brain caused movement, perception, memory and emotions -- but what he didn't find.
Penfield could find no part of the brain that, when stimulated, caused patients to think abstractly -- to reason, think logically, do mathematics or philosophy or exercise free will.
He noticed the same thing about epileptic seizures as about stimulation during surgery. Patients who were having seizures did all sorts of things -- they jerked their muscles, they saw flashes of light or had unusual sensations on their skin. They even occasionally had specific memories and emotions. Then they fell unconscious.
But patients never had intellectual seizures. That is, they never had seizures that caused them to reason, think logically, or do mathematics or philosophy. There are no "calculus seizures" that cause them to uncontrollably take first derivatives. There are no philosophical seizures that cause them to uncontrollably contemplate Plato's Republic.
Penfield asked the obvious question: why did brain stimulation only cause certain mental operations, like movement, perception, memory and emotion to happen, but not other ones, like abstract thought and free will? As Denyse O'Leary and I discuss in The Immortal Mind (Worthy June 3, 2025), he eventually came to the obvious conclusion: he couldn't evoke abstract thought or free will by stimulating the brain because abstract thought and free will don't come from the brain.
Penfield started out as a materialist, like most scientists do, but, as he learned more about the mind and the brain he became a dualist. He concluded in his book Mystery of the Mind (1975) that the mind is something separate from the brain, and that there are aspects of the mind that don't come from the brain but are spiritual in nature. As he put it, "The mind must be viewed as a basic element in itself . . . That is to say, it has a continuing existence." (p. xxi.)
Many other neuroscientists have followed in Penfield's footsteps and their research points to the very same conclusion. That said, within the neuroscience community materialism reigns so it is unfashionable (and dangerous to a scientists' career) to admit the truth about dualism. Neuroscience shows us that the brain is an organ, like the heart or the liver, that has specific jobs to do. The brain orchestrates our bodily processes (sometimes called vegetative functions) -- our heart rate, our blood pressure, our hormone levels and so on. The brain is the source of our ability to move, to perceive, to remember and to have emotions.
Neuroscience shows that intellect and free will are spiritual powers of the human soul. Our spiritual powers depend on the brain and body for our normal functioning -- e.g., we can't reason well after being hit on the head with a baseball bat and we don't always exercise our free will wisely when we've had too much alcohol. The brain, that is, is necessary and sufficient for our embodied powers -- vegetative, locomotor, perceptual, mnemonic, and emotional -- and the brain is necessary but not sufficient for the normal exercise of our intellect and our free will.
The human soul is an embodied spirit, a composite of bodily and spiritual powers. We are created by God with some abilities that are physical and some abilities that are not strictly physical -- i.e., that are spiritual, created in His Image. This insight is actually quite ancient. It was an insight of many great classical philosophers and theologians, Plato, Aristotle, Augustine, Aquinas, and countless others. What is remarkable in our day is that this profound and true understanding of the human soul -- our spiritual soul -- is now being confirmed by modern neuroscience.