“Cogito, ergo sum,” the great French mathematician and philosopher Rene Descartes (d. 1650) famously wrote. “I think, therefore I am.”
Pursuing what is often called his “method of systematic doubt,” Descartes tried to base his philosophy on something that he knew with absolute certainty to be true. And that turned out to be the fact that he was thinking. He reasoned that even if he doubted that he was thinking, the very fact of his doubting it proved that he was thinking. And if he was thinking, he existed. Of that, he could be completely sure. However eccentric it may be to do so, I can doubt the existence of other minds. (Perhaps I’m surrounded by cunningly designed organic robots who merely simulate emotion and thought.) But I can’t coherently doubt the existence of my own mind.
Exactly what it means to “think,” however, remains deeply mysterious.
The German biologist Karl Vogt (d. 1895) once explained, “The brain secretes thought as the stomach secretes gastric juice, the liver bile and the kidneys urine.” But if this is true, it’s exceedingly strange — and it’s strange for at least three reasons.
The first reason is that while thoughts are “about” something — we think about poetry, for example, or God, or earning a profit, or plotting a devastating chess move — gastric juice, bile and urine are not “about” anything. While we can intelligibly describe an astronomer as thinking about Mars, it makes no sense whatsoever to describe a merely physical process as being “about” anything else. A cook may boil water to make soup, but the water isn’t boiling about minestrone.
The second reason relates to the subjective experience of thinking. Consider, for example, a mountain stream flowing downhill. Given enough time and patience, we could exhaustively describe the stream; there would be nothing left over: It flows because of gravity. Its water comprises hydrogen and oxygen, accompanied by whatever minerals or other contaminants it may have picked up along the way. It takes its particular course because of the nature of the terrain through which it flows.
Try, though, to give an exhaustive external description of brain activity. Even if you were to succeed, the most important fact about consciousness — self-awareness, inwardness or subjectivity — would elude such description. Another person can record your reactions to pain, but she doesn’t feel your pain. A neurologist can describe how different portions of your brain light up as you feel that pain or hear a symphony, but his external description won’t give him your unique experience of the pain or of that symphony. Whereas the river presumably has no inner experience, you do. This is the miracle of consciousness, of subjectivity. Although you can describe your thoughts or emotions more or less adequately, they cannot actually be transferred to another. In this sense, at least, John Donne’s statement that “no man is an island” is demonstrably false.
The third problem is that Vogt’s opinion seems to reduce thinking to nonsense, and to undercut itself. Stomachs, livers and kidneys secrete their products according to determinate biochemical laws. Likewise, a stream flows according to predictable natural principles.
But if “thoughts” are actually biochemical products just like stomach acids, bile and urine, and if they’re determined by preceding biochemical brain states according to predictable laws, just as those other secretions proceed from the prior states of their respective organs, it’s very difficult indeed to see why we should trust them or imagine that they convey truth. Why should we grant any more intellectual authority to the secretions of Vogt’s brain (or, for that matter, of our own) than we do to the products of his stomach, liver or kidneys?
A breeze blows according to complex though determinate laws. But it doesn’t blow “about” anything. It doesn’t experience subjective self-awareness. And it would be mere poetic metaphor, at best, to describe a breeze as true, false, happy or upset.
Some, consistently following materialism to its logical conclusion, have denied the reality of consciousness, declaring it an illusion. But surely, as Descartes understood, consciousness is the one thing that absolutely cannot be an illusion, the one thing to which we have direct and undeniable personal access.
The mystery of consciousness is a remarkably difficult one, and maybe irreducible. Religious believers can perhaps be pardoned for suspecting that it points to something at the very foundation of the universe that isn’t merely mindless matter and energy.
Daniel Peterson teaches Arabic studies, founded BYU’s Middle Eastern Texts Initiative, directs MormonScholarsTestify.org, chairs mormoninterpreter.com, blogs daily at patheos.com/blogs/danpeterson and speaks only for himself.