Locke on ideas of substance and the veil of perception

John Yolton has argued that Locke held a direct realist position according to which sensory ideas are not perceived intermediaries, as on the representational realist position, but acts that take material substances as objects. This paper argues that were Locke to accept the position Yolton attributes to him he could not at once account for appearance-reality discrepancies and maintain one of his most important anti-nativist arguments. The paper goes on to offer an interpretation of Locke's distinction between ideas of substances and modes, a distinction that helps Locke to explain appearance-reality discrepancies, although not in a large enough range of cases to strengthen Yolton's interpretation.