Richard Swinburne on Science and Secondary Qualities
All reduction from one science to another dealing with apparently very disparate properties has been achieved by this device of denying that the apparent properties (i.e. the "secondary qualities" of colour, heat, sound, taste, etc.) with which one science dealt belonged to the physical world at all. It siphoned them off to the world of the mental. But then, when you come to face the problem of the sensations themselves, you cannot do this. If you are to explain the sensations themselves, you cannot distinguish between them and their underlying causes and only explain the latter. In fact the enormous success of science in producing an integrated physico-chemistry has been achieved at the expense of separating off from the physical world colours, smells, and tastes, and regarding them as purely private sensory phenomena. The very succes of science in achieving its vast integration in physics and chemistry is the very thing which has made apparently impossible any final success in integrating the world of mind into the world of physics.