Most foul odors we smell that give us all a shock of disgust seem to come from bacteria (at least before our mastering of chemistry). We can explain this evolutionarily as a means for making us avoid the most salient disease vectors from our humble origins (excreta, spoiled meat, putrid water, etc.). My question is this, did the selection pressures of evolution act to assign the awful olfactory sensations to the particles emitted by dangerous bacteria and their waste, OR did we evolve the response of disgust to those already-assigned sensations? In other words, does my dog experience a COMPLETELY DIFFERENT SENSATION when smelling (and rolling in) a dead animal - one that's not so bad, or does he experience the smell like I do he just LIKES IT BETTER than I do? I think this question might be about qualia, and whether there's a two-step process in how we perceive them. Do evolving organisms just shift around the few bad smells there are to the stimuli that best deserve them, or are smell sensations and...

"Different qualia or different attitudes to the same qualia?" That seems an intractable question. It should make us suspicious. Maybe the very idea of qualia (as postulated by some philosophers) is the source of the problem. For sceptical thoughts along these lines, see Dan Dennett's justly famous paper, "Quining Qualia", readable here .

Are rainbows real? That is, do they exist unperceived?

The Guinness Book of Records says (or at any rate, used to say) that the world’s longest lasting rainbow was continuously visible over Sheffield for some six hours on 14 March 1994. Here's a picture (I had an office in the Arts Tower at the time which is why I know about it!) Now, did the Book of Records do some research to check that at every single second from 9am to 3pm, someone or other was perceiving the rainbow? I very much doubt it! I guess that the Book of Records supposed that, to establish the record, it was enough to have grounds for thinking that,at any moment in those six hours, someone suitably placed and lookingin the right direction would have seen the rainbow (it was continuously perceiv able , though not necessarily continuously perceived). And the Book of Records is speaking here entirely in accordance with our ordinary ways of talking about rainbows as continuing to exist unperceived. I see a dramatic double rainbow, go to fetch someone to see...