I got in an argument with a philosophy professor. He put a stick in water and said 'look... the stick is broken'. I said "no, the stick is not broken. it appears broken because the index of refraction is different in water than air, which causes light to bed". he didn't like that very much. It's still not clear to me what point he was trying to make (that human senses are limited?)
you were of course correct, but your professor was simply illustrating a point- of whether we can trust our senses, of how we truly "know" something. philosophy often brings up "commonsensical" questions such as these. he probably didn't reply to you because he was bored from hearing the same smart alecky response every year :)
If that was his point, there are far better ways to argue for it (specifically, Descartes' great deceiver). There was nothiing smart alecky about my response- just touching the stick, or pulling the stick back out, would verify that it was not broken.
