Introduction to the Special Issue on Multisensory Perception in Philosophy.

European philosophers of the modern period generally acknowledged that the senses are our primary source of knowledge about the contingent states of the world around us. The question of modality was of secondary interest and was very little discussed in this period. Why? Because these philosophers were atomists about sense-perception, an attitude that makes multisensory perception impossible. Let us explain. Atomists hold that all sense-experience is of ‘ideas’ — a somewhat oversimple, but still useful, way to think of these is as images. All ideas are ultimately composed of simple ideas. Atomists hold, moreover, that the intrinsic nature of a simple (or non-composite) idea is fully given by conscious experience of that idea, and in no other way. For example, burnt sienna is a simple idea because it is not composed of other ideas. Nothing about its intrinsic nature can be known except by experiencing it — a colour-blind individual cannot know what it is. It is, moreover, adequately and completely known when it is experienced; there is nothing more to know about it than is given by visual experience of it (see Note 1). Now, on this account of simple ideas, distinctions among them cannot be analysed. For atomists, inter-modal distinctions, like all other distinctions among ideas, are primitive and based in experience. What, for example, is the difference between burnt sienna and the sound of a trumpet playing middle C? All that can be said is that they are experientially different from one