Most bathroom sprays don't destroy bad odours so much as overpower them with a more pleasant odour. In such cases, can people really be said to be smelling the bad odour if they have no conscious awareness of it?

Philosophers will divide over the question whether tastes, colours, sounds, smells and so on are by nature physical or phenomenal. If these so-called "secondary qualities" are physical, then it makes sense to think of one smell covering up another, which is still there and reappears when the smell covering it up is removed. Similarly, if you think of colour as a physical entity, or you thinkbof it as rather like paint , you can think of one "colour" covering another up, so that the top layer of "colour" could be peeled off to reveal the older underlying colour. But if you think of the qualities as inherently perceptual, then one colour or sound or smell is not covered up by another; it is replaced by it. As Plato puts it in the Phaedo, 'in such a situation it either withdraws or ceases to exist.' My own preference is for a theory in which the "secondary qualities" like tastes are not inherently physical. It makes no sense to think of a physical blue, say, that lacks the quality blue. But good arguments can be advanced for both views.

Read another response by Jonathan Westphal
Read another response about Perception, Consciousness