30 August 2006

The extent of our non-inferential knowledge is remarkable. I can perceive differences, pick up on trends and follow social norms, all without making a single, conscious entailment. Does she like me? The answer is yes. It is as evident to me as the colour of this table.

Philosophers suppose our perceptual contact with the world is a process. Light refracts off an object, and it stimulates my rods and cones. That stimulation gets converted into neural pusles. They soar through my nervous system, and I detect a colour. But why think that those lower-level processes play any role in my perceptual life? Yes, they are dependent on them; the colours I perceive are constrained by the mechanics of my visual system. But psychology is one thing, physiology another. Those pulses play no role in my perceptual life, and so neither should the light, the object itself or its precise qualitiative features.

Our perceptual lives, as Descartes aptly identified, are independent from our physiological lives. The red I see is incommensurably characterised with scientific predicates.