Hold That Tiger

Galileo Unchained posted an entry on Alvin Plantinga's evolutionary argument against naturalism.  As I understand it, this argument is that if evolution and naturalism are true that we have no reason to believe that our perceptions are accurate.  Since it is perceptions that lead some people to arrive at evolution and naturalism this posture is self defeating.  We would have no reason to believe that our beliefs were accurate.  Hence it would be unreasonable to take such a position.

While I disagree with Plantinga's conclusion, the argument presented against it seems incomplete.  It is simply the assertion that accurate perceptions would lead to survival.  While I agree with this, I think that we need to put more time and effort into dealing with Plantinga's argument to the contrary.

Plantinga rightly points out that it is our behavior that leads to survival and reproduction and not our beliefs.  He gives an example of a man who wants to be eaten by a tiger and believes that the best way of accomplishing this goal is to run away from the tiger.  Evolution will favor his sophisticated mental apparatus that led to such a belief, since it will motivate him to run away from the tiger and survive.  Ironically, if he were to develop the more accurate belief that running toward the tiger would improve his odds of being eaten, then this would hurt his chances of survival since it would motivate him to run toward the tiger.

I wonder if Plantinga shouldn't rather imagine that being eaten by tigers improves our health, but that when we think we see a tiger we are really seeing the absence of a tiger.  Hence we are continuously dined on by tigers and enjoy the good health effects that naturally result.  We just don't think that we are being eaten by tigers, because our perceptions don't properly reflect reality.

But what kind of perceptions of reality would we need to have?  Suppose that in the real world all objects are only where they appear to be absent.  In such a world our perceptions would be like a negative image in photography.  There would still be a one to one correspondence between perceptions and reality.  This would be no more serious than our seeing the world upside down or backwards and then reversing the image in our heads.  I'm not sure that this should count as inaccurate perception.

It is unlikely that the man's perception of the tiger is formed ad hoc.  That would violate parsimony.  It is likely that the same faculties that enable him to perceive the tiger enable him to perceive other things.  Hence the very thing that would cause one inaccurate perception would be likely to lead to others.  It is the man's perceptions combined with his values (and perhaps other things) that lead to particular behaviors.

It is not enough for the man to simply value things that lead to health, or to have an aversion to them coupled with inaccurate perceptions.  He will have to be able to weigh one outcome against another in order to pick the best one (or worst one).  In order for him to have a set of values that would meet all of his needs it would have to help him make decisions in a wide variety of situations.  It would have to enable him to weigh each outcome against a great many competing outcomes.

Our faculties must be reasonably simple.  It certainly seems like we use the same set of eyes to see both tigers and everything else that we see.  To believe that this perception is inaccurate would violate parsimony. Similarly we can rule out the world where tigers are only where they appear to be absent.  Objects appear to be in specific places and are absent from everywhere else.  From this it follows that objects are more or less where they appear to be and have roughly the shape that they appear to have.

Perhaps I have overstated the case when I said that it follows.  Our belief in evolution comes from observations that we have made.  If our perceptions are unreliable, then the theory of evolution would be as well.  Hence someone might object that my approach is question begging.  However, this is not my intent.  We are justified in believing that our perceptions are reasonably accurate because if we believed otherwise we could not form reasonable beliefs.

My argument is intended to counter Plantinga's reductio ad absurdum.  It is his burden to show that evolution and naturalism form a self defeating set of beliefs.  By showing that evolution would be likely to lead to reasonably accurate perceptions, I counter that argument.  Plantinga has failed to meet the burden, and so we must reject his argument.