I’m going to comment on some statements in this post:
Scientific evidence shows that consciousness and personality are highly dependent upon the brain. Nothing mental happens without something physical happening.
That’s a very demanding claim. Do we have anything approaching evidence for a one-to-one correspondence between mental events and brain events? For instance, brain scans are sometimes cited as evidence, but that seems to be quite ambivalent:
That strongly implies that the mind cannot exist independently of physical arrangements of matter. In other words, we do not have a soul. And this is exactly what we would expect if naturalism is true.
Well, according to eliminative materialism, what we’d expect if naturalism is true is that we don’t even have mental states:
So Jeff is playing with matches in a gas station.
But if theism is true, then our minds should not depend on our brains for their existence; we should have souls.
Christian theology has different theories of the soul. For instance, the soul in Thomism is quite different from the soul in Augustinianism.
Michael Tooley has summarized the evidence as follows:
First, when an individuals brain is directly stimulated and put into a certain physical state, this causes the person to have a corresponding experience.
A corresponding experience of what?
From TV shows I’ve seen, you have neurosurgeons operate on fully conscious patients (since the brain can’t feel pain), and solicit feedback from the patient as the surgeon is operating on his brain. To me, that seems dualistic.
Second, certain injuries to the brain make it impossible for a person to have any mental states at all. Third, other injuries to the brain destroy various mental capacities. Which capacity is destroyed is tied directly to the particular region of the brain that was damaged.
Jeff is using a computer to communicate with the outside world. He’s also using a compute to learn about the outside world. Conversely, his computer allows other people to contact Jeff. So it’s a two-way street.
If Jeff’s modem were damaged, he’d be sealed off from the world in that respect. But that would just mean the medium or conduit was blocked.
Fourth, when we examine the mental capacities of animals, they become more complex as their brains become more complex. And fifth, within any given species, the development of mental capacities is correlated with the development of neurons in the brain.
Isn’t it really that simple or direct? Let’s take a few examples. In my observation, little dogs can be smarter than dogs 10, 15, 20 times their size. The bigger dogs have bigger brains, yet they’re dumber than the smaller dogs. Do the smaller dogs have more complex brains?
On a related note, some dog breeds are smarter than others. But does that correlate with canine brain capacity?
Social insects do very ingenuous things. If social insects were the size of chimpanzees (a scary thought!), it would be tempting to attribute their ingenuity to their brainpower.
Likewise, predatory insects mimic the behavior of predatory mammals. Stalking their prey. Or ambush predators. When wolves, lions, leopards, and Cape hunting dogs do this sort of thing, it’s tempting to chalk that up to their mammalian brainpower.
But that explanation won’t work for insects. You may say it’s due to “instinct,” but that’s just a verbal placeholder. It doesn’t really explain anything. At most, it pushes the issue back a step. Where is this “instinct” stored in the nervous system of an insect? How does the nervous system of an insect have the capacity to store such complex information?
I don’t deny that souls and brains affect each other in subtle, intricate ways. But it seems to me that Jeff is appealing to half-truths. Ignoring counterevidence and oversimplifying the interrelationship.
In response, I have made a couple of minor changes to the informal statement at the beginning of the post. I've also added an entirely new section for objections to premise (2), plus a discussion of a new objection to premise (1).
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Jeffery Jay Lowder said:
ReplyDelete"Second, certain injuries to the brain make it impossible for a person to have any mental states at all. Third, other injuries to the brain destroy various mental capacities. Which capacity is destroyed is tied directly to the particular region of the brain that was damaged."
At best this is pretty simplistic. To take an example, two people may have the exact same pathological process which in turn affects the exact same region of their brains but have entirely different outcomes. An elderly person who had a stroke which destroyed half his or her brain would have a lot more difficulty recovering brain function (which of course is an important "mental states" indicator) than a couple of months old fetus who had a stroke in utero which likewise destroyed the exact same half of his or her brain. For instance, check out this story. Here is the original PNAS article too.
Neurologists and neuroscientists argue this is largely due to neuroplasticitiy - i.e. the brain's ability to repair itself by rewiring and remapping itself. The major differential in an elderly person demonstrating poor recovery while a fetus could have normal brain function at birth seems to be age. The neurophysiological changes (among other changes) entailed in the aging process seems to be an important determinant in how pliable the brain is to rewiring and remapping itself.
Anyway, all this to say, given brain plasticity, it's not necessarily the case that brain function or capacity is "tied directly to the particular region of the brain that was damaged."
Jeffery Jay Lowder:
ReplyDelete"Fourth, when we examine the mental capacities of animals, they become more complex as their brains become more complex. And fifth, within any given species, the development of mental capacities is correlated with the development of neurons in the brain."
Again, this is all pretty simplistic. For starters, what does Lowder mean by "complex"? And what does he mean by "the development of neurons in the brain"?
The number of neurons? The size of neurons? The mass of neurons? The connections made by neurons?
Is he referring to the number or length or diameter or other characteristic of axons and/or dendrites on each neuron?
What about myelination which hugely affects the speed of action potential propogation between neurons?
Also, there are a tremendous variety of neuronal types. Why the blanket statement to include all neurons?
Moreover why is the focus on neurons alone? What about glial cells? After all, neurons are only a small fraction of all the cells in the brain. Glial cells make up the vast majority. And there are various glial cells as well. (Although if we want to be more conservative then there would still roughly be an equal amount of glial cells to neurons.)
What about the blood vessels which supply the neurons in our brains? For one thing, that's what fMRI primarily measures: change in blood flow. For another, blood vessels constitute about 20% of the brain's volume. And the brain receives about 15-20% of the cardiac output for the entire body.
What about hormones which influence the brain and also by which the brain influences other parts of the body?
And let's not forget to include neurotransmitters.
Many animals have many of these as well.
So why aren't any of these factors part of the assessment? Since they're not, it's pretty simplistic to say what Lowder has said.
Obviously this is an imperfect (and maybe even poor) analogy but hopefully the gist of what I'm trying to say comes across: it's sort of like saying houses get more complex as their master bedrooms get more complex and the development of houses is correlated with the development of walls in the master bedrooms. But there's so much that's left unsaid and there's so much that's still to be said.
Thread continued here.
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