If eyes had never evolved, would LIGHT still exist (or: be manifest)? By this I do not mean: would there still be electromagnetic radiation of a certain range of wavelengths (there would, of course). Rather, I mean: in the absence of eyes, would there still be brightness, luminance, illumination (i.e. what we ordinarily call 'light')? I am aware of course that, according to physics, light simply IS electromagnetic radiation of a certain range of frequencies. However, does this mean that things are, so to speak, illuminated "in themselves"? Or, contrariwise, is it the case that, in order to get what we ORDINARILY call 'light' (brightness, luminance etc., as opposed to Maxwell's equations), we must also take into account the way that electromagnetic waves excite our rods and cones etc.? In other words, without eyes -- and, therefore, without VISIBILITY -- would the entire universe remain 'in the dark'? Does it indeed make any sense to speak of the universe being either 'dark' or 'illuminated' in the...

I think you've pretty much answered your own question. You see (get it?) that light could exist even in the absence of any creatures sensitive to it. And of course in such a situation, there would be no one and nothing experiencing the light. So is anything visible ? "Visible," like many English words that end in "ible," "able," "uble," or "ile," picks out what philosophers call a "disposition" -- a condition of being ready, so to speak, to cause certain things to happen, or to undergo certain changes, if certain conditions are met. Salt is sol uble -- that means that if it's put into a pot of water, then it will dissolve. Waterford crystal is frag ile -- if you drop it, it will break. Similarly, to call an object vis ible is to say that if it is illuminated, and if a creature that is sensitive to light points its sensitive parts toward the object, then the object will cause the creature to have visual experiences (by bouncing the light onto the creature's...