Existence

Do rainbows exist? I assume rain drops and sunlight exist, but the rainbow is not a collection of rain drops, nor a region of the atmosphere where passing rain drops get some colour, is it? Should we say that rainbows are optical illusions? Or what?

Comments

Lots of things should be said to exist, even though they are not material entities (like raindrops) nor energy forms (like sunlight). We're happy to talk about numbers or abstract concepts as existing, for example, and likewise dreams, or things that happened in the past. We might provisionally say that X exists if it were to matter in some way if someone asserted that X did not exist. (This is a pragmatist definition. I'm not endorsing it so much as finding it useful.) If someone said that you DID NOT have the dream last night you say you had, then that would matter, because they would be saying you are lying; if someone says that we have no concept of causation (Hume), then that matters because whole bits of philosophy, and maybe physics too, become valid or invalid. An optical illusion exists because its happening matters to the person experiencing it. (So, even an atheist would have to admit that God existed, because it matters so much to so many that he does; however, the atheist would assert that God exists more in the way of rainbow or dream, than in the way of a rainbow.)

To my mind, the interesting question is not 'what kinds of things can be said to exist?' but rather 'what different types of existence are there, how do they relate together, and how is it we come to understand such a variety of types?'

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