Page 78 - Darwin's Dilemma: The Soul

Darwin’s Dilemma: The Soul

its own type of stimulus: molecules, waves or vibrations. But the
answer does not lie here, because despite their wonderful variety,
each organ does essentially the same job: it translates its particular
type of stimulus into electrical pulses. A pulse is a pulse is a pulse. It
is not the colour red, or the first notes of Beethoven’s Fifth—it is a bit
of electrical energy. Indeed, rather than discriminating one type of
sensory input from another, the sense organs actually make them
more alike.
All sensory stimuli, then, enter the brain in more or less undifferen-
tiated form as a stream of electrical pulses created by neurons firing,
domino-fashion, along a certain route. This is all that happens. There
is no reverse transformer that at some stage turns this electrical ac-
tivity back into light waves or molecules. What makes one stream in-
to vision and another into smell depends, rather, on which neurons
are stimulated. 44
This is truly astonishing and significant. All the sensations,

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