Jonathan Westphal

This chapter focuses on the incompatibility of afterimage colors. Several quasilogical, semantic, and metaphysical questions having to do with incompatibility come up in color theory, and the problem is so complicated and fragile that it is argued here that, despite some marvelous work on the topic, the problem remains to be sorted out. Every naive subject who encounters afterimages without prejudice has agreed that they have color; this is mentioned here because it is the initial and also the commonsense view. However, accepting that a physical account of color incompatibility is right for physical colors makes an account for the incompatibility of afterimage colors improbable. One can provide a physiological account based on opponent processes, but this will deliver only a contingent truth or a necessity relative only to a particular retinal structure and postretinal neural coding.

Dans la première méditation, Descartes a conclu, en regard des songes, « qu'il n'y a point d'indices concluants, ni de marques assez certaines par où l'on puisse distinguer nettement la veille d'avec la sommeil [...] » . À la fin de la sixième méditation, il a conclu qu'il y a de tels indices, mais qu'on a besoin de la garantie de Dieu pour savoir si ces indices sont réellement des indices de la veille. Cottingham a proposé une objection générale contre tels indices de la veille: On peut rêver cet indice. Selon les raisonnements de Cottingham, il s'agit de l'existence de l'indice. Or, chez Leibniz et Descartes il ne s'agit pas de cela, mais il est question de savoir si l'indice est vraiment un indice de la veille. La prétention que l'indice puisse être présent en songe fait une pétition de principe. Notre examen des indices que Leibniz et Berkeley ont proposés révèle cette pétition

The world as we experience it is full of colour. This book defends the radical thesis that no physical object has any of the colours we experience it as having. The author provides a unified account of colour that shows why we experience the illusion and why the illusion is not to be dispelled but welcomed. He develops a pluralist framework of colour-concepts in which other, more sophisticated concepts of colour are introduced to supplement the simple concept that is presupposed in our ordinary colour experience. The discussion draws on philosophical and scientific literature, both historical and modern, but it is not technical, and will appeal to a broad range of philosophers, cognitive scientists and historians of science