Some of the ideas here border on Solipsism, so I thought I'd post this again, here:
MRC_Hans' practical test of Solipsism .(tm)
Disclaimer: This experiment might not only bruise your ego, but also your body, so you undertake it entirely at your own risk. I will not be held responsible for any consequences, including, but not limited to, loss of pride, peace of mind, teeth, etc.
1) Find a busy city street.
2) Wait for large aggressive looking male to walk by (generally, the more tattoos, the better).
3) Walk up behind said large aggressive looking male and direct a solid kick at the lower, rear portion of his body.
4) When he turns, tell him: "That was because you mother is so ugly".
5) Observe.
You will soon have tangible evidence for the following:
a) You exist physically.
b) At least one other entity exists physically.
c) You and that other entity are in communication, both abstractly and physically.
d) The other entity probably has a mother.
You may conclude that all your observations are, after all, part of an illusion, but the experience should convince you that you had better
treat the illusion as reality .
Good luck!
Hans