Ennead IV 5[29] has been poorly served by translators and commentators, misreporting what Plotinus wrote and, with these mangled results, asserting that this part of his treatise on the “Problems about the Soul” is merely a disjointed series of doxographical fragments with little compelling contribution to make. More careful translation and analysis reveal something strikingly different and original. First, he gives a cogent critique of the theories of Plato and Aristotle concerning the body between and the role of daylight. Second, (...) he substitutes his own account in terms of both sympathy and the principle of two acts, explaining vision both during the day as well as at night, notably deficient in previous accounts. Third, he derives some surprisingly original corollaries about the nature of light and the source of color. (shrink)