At one time it was common for philosophers to pay scant attention to science. Many preferred to analyze issues through sheer intellectual prowess. But today most philosophers of mind study neuroscience carefully, looking for clues about the nature of consciousness. I’m going to post several entries about mind and brain, starting with comments about the astonishing capabilities that are packed into a few inches of cranial space.
The human brain contains about 100 billion nerve cells. The word “cell” may seem to imply simple shapes, like little boxes, but neurons look more like bushes or trees, with luxuriant branches and tendrils projecting from the cell body. One winter’s day while driving through the countryside I realized that every one of the bare trees lining the highway looked roughly similar to an individual neuron. So next time you’re in a forest or a botanical park, imagine that you’re looking at your own inner “garden.”
Popularized descriptions of the brain tend to be simplistic. When authors refer to brain structures such as channels, pumps, and receptors, they are talking in almost cartoon-like fashion. According to George Johnson, these terms are more like metaphors than like literal descriptions of molecular processes. He says that “faithfully simulating a single neuron would take an entire supercomputer” (In the Palaces of Memory, p. 99). So just one of your nerve cells is as complicated as a computer, and you have roughly 100 billion of them!
Furthermore, the basic building block of brain power is not the individual nerve cell. It’s the synapse, the connection between the cells, and your brain contains at least one hundred trillion of these linkups. Suppose you started counting the links between neurons in your brain, one connection every second, twenty-four hours a day. At the end of a year you would have counted around thirty million. But to count all of the interconnections would take you over three million years.
Can you see why each person is unique? Can you see why we might have amazing abilities? As one neurologist exclaimed, “100 trillion different connections – hell, you can do anything with that. That’s more than enough to contain a soul” (quoted by Hooper and Teresi, The Three-Pound Universe, p. 31, emphasis added).
And that’s just the beginning. We’ve been talking about how many connections there are in your brain at this instant, but these connections are changing all the time. How many possible sets of interconnections could your brain have? Philosopher Owen Flanagan has suggested that the number of possible link-ups in the average brain is ten to the one hundred trillionth power (Consciousness Reconsidered, p. 37). The brain is, indeed, a very big place in a very small space.
I have come to realize that I am inside of this huge little thing, and this giant-brain perspective has revolutionized the way I think of consciousness.
Roger Christan Schriner