I cant prove that you exist to me anymore than i can prove that I exist to you. We are each our own universes, creating and destroying people as we move around. But surely other people exist that we've never met, their actions can be seen, heard, ect. For example, we know our mail gets delivered, yet do see the mailperson? If no, does he/she exist to you in any other form other than the fact that you receive mail? Is it any different than water coming out of your shower? If yes, have you seen his/her face? Would you be able to recognize him/her among the other faceless mass you walk past? If yes, do you know his/her name or family status, his pleasures or pains? Has he/she made you think about him/her at times other that when you see them, good or bad? If yes, congratulations he/she exists to you, your universe is slightly larger and more populated. [spoiler] ( ͡° ͜ʖ ͡°) [/spoiler]