Wednesday, 14 April 2010

Moths to the Flame

Many people agonise over the meaning of life. Why are we here? Where are we going? What's it all about, Alfie?

There's an assumption to theism of ultimate meaning, and individual personal meaning, that is satisfied in the concept of an afterlife in heaven. If we return to dust, what's the point of getting up in the morning? (This argument is deeply flawed on a number of levels, but let's put that to one side.) But *why* do we seek this meaning, if it results in such false beliefs, a theist might ask. False beliefs aren't beneficial to survival, so this wouldn't be naturally selected.

I see two answers to this apparent conundrum. Firstly, meaning-seeking has been extremely useful to homo sapiens; we are a (perhaps the only one, so far) being that tries to uncover why things are the way they are. It's difficult to see how technology could be achieved *without* such a tendency. So it's certainly *conceivable* that meaning-seeking has been selected for its own good. Secondly, it may just be a by-product of advanced brain functions that have been selected for other reasons.

Are these explanations plausible? I think so; we can see a simple example of other *behaviour* that has been naturally selected and causes problems despite that. If we light a candle outside we see many insects 'foolishly' flying into the flame, like kamikaze pilots (and what about *that* behaviour?!). Richard Dawkins as usual writes well on the subject:
Moths fly into the candle flame, and it does not look like an accident. They go out of their way to make a burnt offering of themselves. We could label it “self-immolation behavior” and wonder how Darwinian natural selection could possibly favor it. My point, again, is that we need to rewrite the question before we can even attempt an intelligent answer. It is not suicide. Apparent suicide emerges as an inadvertent side effect. Artificial light is a recent arrival on the night scene. Until recently, the only night-lights were the moon and the stars. Being at optical infinity, their rays are parallel, which makes them ideal compasses. Insects are known to use celestial objects to steer accurately in a straight line. The insect nervous system is adept at setting up a temporary rule of thumb such as, “Steer a course such that the light rays hit your eye at an angle of 30°.” Since insects have compound eyes, this will amount to favoring a particular ommatidium (individual optical tube radiating out from the center of the compound eye). However, the light compass relies critically on the celestial object being at optical infinity. If it is not, the rays are not parallel but diverge like the spokes of a wheel. A nervous system using a 30° rule of thumb to a candle, as though it were the moon, will steer its moth, in a neat logarithmic spiral, into the flame. It is still, on average, a good rule of thumb. We do not notice the hundreds of moths who are silently and effectively steering by the moon or a bright star or even the lights of a distant city. We see only moths hurling themselves at our lights, and we ask the wrong question. Why are all these moths committing suicide? Instead, we should ask why they have nervous systems that steer by maintaining an automatic fixed angle to light rays, a tactic that we only notice on the occasions when it goes wrong. When the question is rephrased, the mystery evaporates. It never was right to call it suicide.
What Use Is Religion?
Whenever someone bemoans the nihilism of atheism, I see a moth fluttering into the flame.


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    彭昱宏 says:
    17 April 2010 at 07:44

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