Idly glancing at a bookshelf in our house a few days ago, I noticed a book that I bought back in 2010, Paul Thagard's "The Brain and The Meaning of Life." Since, I've been re-reading some of it each morning.
Great book, with some great ideas. I blogged about these before in "Reality is real, but brains construct knowledge" and "Divinity isn't necessary to make life meaningful."
Here's an excerpt from the first post.
When we go on our evening walk, my dog has a very different experience of reality than I do, given her vastly superior sense of smell. As I stand holding the leash, waiting for her to finish a comprehensive sniffing of a clump of grass that looks to me just like all the other clumps along the road, she is engaged in tasting an odor feast that's beyond my comprehension.
So we Homo sapiens do indeed construct our knowledge of reality through the only means available to us: the human brain. Thagard reviews some hypotheses about how we do this, and arrives at a favored theory: inference to the best explanation.
Don't be thrown off by this fancy phrase.
It's what we all do every day of our lives. Recently my wife excitedly told me that I had to come and see what was being done to a cherished twenty year old vine maple tree that is a centerpiece of our landscaping.
Bark was being chewed off. Not just a little. A lot. Some large branches were almost girdled, which could kill them. We talked about what animal could be the culprit. Deer? Raccoons? Ground squirrels?
We immediately suspected the latter, as they've been causing us other problems.
Some Googling revealed that they do indeed like to eat bark, something we hadn't noticed before. So ground squirrels became our inference to the best explanation and we've been acting accordingly to deal with the little furry irritants.
Re-reading Thagard's book reminded me how often he mentions "inference to the best explanation." This strikes me as simple common sense, but the concept has some pretty sophisticated philosophizing behind it.
I could understand the first part of the Wikipedia article on abductive reasoning, a.k.a. inference to the best explanation. The rest of it looked way too complex for me to attempt to fathom. Especially on a pleasant early summer Saturday.
This part I grasped, though.
For example, the lawn is wet. But if it rained last night, then it would be unsurprising that the lawn is wet. Therefore, by abductive reasoning, the possibility that it rained last night is reasonable (but note that Peirce did not remain convinced that a single logical form covers all abduction).
Moreover, abducing rain last night from the observation of the wet lawn can lead to a false conclusion. In this example, dew, lawn sprinklers, or some other process may have resulted in the wet lawn, even in the absence of rain.
Peirce argues that good abductive reasoning from P to Q involves not simply a determination that, e.g., Q is sufficient for P, but also that Q is among the most economical explanations for P. Simplification and economy both call for that "leap" of abduction.
It seems to me that, again, this is an example of common sense being dressed up in fancy philosophical language. As in my ground squirrel example, isn't this what everybody does when faced with a problem that needs figuring out?
Look at evidence. Consider alternative hypotheses that could explain the evidence. Pick the best one. Thagard puts it this way:
Inference to the best explanation in science has the same basic structure as does reasoning in law, medicine, and everyday life.
In all these domains, you should collect as much relevant evidence as you can, consider higher-level hypotheses and alternative ones, and accept the ones that provide the best overall explanation of the evidence.
For example, Thagard argues persuasively, and I agree with him, that "minds are brains" is a better explanation than "consciousness is supernatural."
There is lots of evidence that supports the first hypothesis, ranging from a baseball bat to the head to sophisticated MRI machines. Evidence of the supernatural nature of consciousness is so few and far between, it might as well be considered zero.
Best explanation, of course, isn't the same as desired explanation.
This is where honest respect for factual evidence is important. Thagard explains how motivated reasoning skews good explanations of facts. When we want something to be true, we ignore evidence at odds with that desire.
Sure, it'd be nice to live forever, to continue to exist after death in a non-bodily form. This is why religions are so popular: they promise something that people desperately want, just as a con man does.
However, even religious true believers should admit that when it comes to demonstrable evidence, the inference to the best explanation leads to the conclusion that minds are brains. When the brain dies, so do we.
It'd be nice if reality were otherwise. But reality is real. It isn't nice.
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