 The claim that conceptual art is to be identified less with a perceivable object than with the meaning or idea it aims to convey, gives rise to a host of complex ontological questions. The rejection of traditional artistic media, together with the de-materialisation of the art object, forces us to reconsider what seemed to be relatively uncomplicated aspects of artistic experience. The answers to questions such as ‘Is there in fact any one thing (or set of things) that we must perceive in artistic appreciation?’, and ‘Is it a necessary condition for the existence of an artwork that it have a medium?’ suddenly become a good deal less obvious.