Condillac's Paradox

I argue that Condillac was committed to four mutually inconsistent propositions: that the mind is unextended, that sensations are modifications of the mind, that colours are sensations, and that colours are extended. I argue that this inconsistency was not just the blunder of a second-rate philosopher, but the consequence of a deep-seated tension in the views of early modern philosophers on the nature of the mind, sensation, and secondary qualities and that more widely studied figures, notably Condillac's contemporaries, Hume and Reid, were not ultimately any more successful at developing an account of vision that unproblematically avoids the paradox. In passing, I take issue with Nicholas Pastore's account of how Condillac's Treatise on Sensations deals with the visual perception of form (in A Selective History of Theories of Visual Perception).