Dualism--that the world divides to the mental and the corporeal--is a central tenet in Descartes's philosophy. It is therefore puzzling that Descartes sometimes suggests that certain phenomena--including perceptions, sensations, emotions, called the 'special modes'--belong to neither mind nor body alone, but specifically to the union of the two. It has been suggested that accordingly, we should regard Descartes as a 'trialist' rather than a dualist. I criticize the 'trialist' interpretation, and offer an explanation of the theory of the special modes which reveals it to be perfectly compatible with Descartes's dualism.