well both talking psychologyly the child is afraid of darkness b'coz he/she does not want to face danger . the man afraid of light may be of some illness or again may be he/she does not want to face the dangers of the world . The child will overcome the fear as it grows but its in will power of man to come out in light and face the world
That is such a deep question that one must know the circumstance. Could you be suggesting "The Light" as in enlightenment?
They are not afraid of the dark/light, they are afraid what's in it that may scare them.
some one who knew wht i was talking about :)