The late Oliver Sacks, from the New Yorker essay The Mind's Eye, which later morphed into the last chapter of the book of the same name.
Galton’s seemingly contradictory statements about imagery—is it antithetical to abstract thinking, or integral to it?—may stem from his failure to distinguish between fundamentally different levels of imagery. Simple visual imagery such as he describes may suffice for the design of a screw, an engine, or a surgical operation, and it may be relatively easy to model these essentially reproductive forms of imagery or to simulate them by constructing video games or virtual realities of various sorts. Such powers may be invaluable, but there is something passive and mechanical and impersonal about them, which makes them utterly different from the higher and more personal powers of the imagination, where there is a continual struggle for concepts and form and meaning, a calling upon all the powers of the self. Imagination dissolves and transforms, unifies and creates, while drawing upon the "lower" powers of memory and association. It is by such imagination, such "vision," that we create or construct our individual worlds.
At this level, one can no longer say of one’s mental landscapes what is visual, what is auditory, what is image, what is language, what is intellectual, what is emotional—they are all fused together and imbued with our own individual perspectives and values. Such a unified vision shines out from Hull’s memoir no less than from Torey’s, despite the fact that one has become "non-visual" and the other "hypervisual." What seems at first to be so decisive a difference between the two men is not, finally, a radical one, so far as personal development and sensibility go. Even though the paths they have followed might seem irreconcilable, both men have "used" blindness (if one can employ such a term for processes which are deeply mysterious, and far below, or above, the level of consciousness and voluntary control) to release their own creative capacities and emotional selves, and both have achieved a rich and full realization of their own individual worlds.
