I should think that in a spiritual form he'd be blind, on account of having no eyes. We'd know if he could see with light, at any rate, because the equivalent of his retinas would cast a shadow as visible light is absorbed.
As for seeing outside of the cave, surely that must make navigation exceedingly difficult. We need perception filters to remove superfluous information, or we'd be overwhelmed and unable to perceive anything. Imagine waking up one morning and seeing things as they really are: mostly empty space, with no colour or shade.
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