How can we be sure we're real?

[John]

After quick-fire debates on Facebook, now the London network is to be closed down, I thought perhaps it could be re-launched here.

I have always wondered what makes as so sure we are alive and living, couldn't everything we see, smell, taste, feel and hear just be sensory stimulus?
Is it not possible we are simply brains hooked up to a sitting in a jar somewhere.
I would like to hear some interesting opinions on this and perhaps issues philosophical issues./

[Alexander Zwagerman]

I think, therefore I am. The rest I cannot know, but I must admit I believe some things (so my hands are my hands, but I cannot prove that they are).