FOM: Evolution and reason: reply to Holmes

Wed Apr 1 13:07:15 EST 1998

Your analogy makes the point that evolution can explain how we can be effective
mathematicians without explaining what mathematics is.  This is a valid point
but there is a problem with the analogy.  Yes, evolution can explain vision but
not tell us about the nature of light; but the nature of light is not what we
see.  The study of human vision (informed by evolution among other things) has
revealed that "color qualia" are illusory in a certain sense.  Thus there is no
Platonic "brown" we directly perceive when we look at a brown cow; there is a
mix of photons of various wavelengths impinging on our retinas which is
interpreted as a single color.  (It's important to use a color like brown in
this example to anticipate identification of a Platonic "red" with a wavelength
of red light; there is no "brown light".)  The mapping of light mixtures to
color qualia is clearly specific to us humans.  What mathematicians have to
defend against social constructivists is the proposition that the integers (for
example) are not like color qualia, which neurologists successfully "reduced
away". "Four" (or "Pi", etc.) has a stronger existence as a concept than "red"!

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