The best way to respond to radical skeptics (those who demand absolute certainty and reject the idea of truth as is commonly understood):


"I don't know if you exist - someone might have hacked into your email account and is impersonating you, you might be a false personality created by some bored 8 year old, you might be a zombie, you might not even exist (and be a computer program who is responding to me) - or we might all be brains in vats.

In that case, I cannot be certain that you do exist and are who you say you are and that I am who I think I am.

In which case all conversation and action becomes meaningless.

I think I shall go and kill myself now."