What do you say to someone who refuses to believe in anyting unless he can prove it with his his five senses (hearing, smelling, seeing, feeling, and tasting)? This is what you call the classic empiricist.

(Empericism is the doctrine that the only things we can know are those things that we experience with our senses). He's a "show me" man. But ask him a few questions. listening carefully, and you'll quickly discover that he believes in many things that have not and cannot be proven by one's senses such as mathematics, beauty, logic, and morality. 

But here is the tallest wall an empericist crashes into: his own view of the world (that nothing can be proven unless it can be physically experienced) cannot be tested empirically. He says that nothing can be known unless it is physically experienced, yet this belief cannot be tested with his senses, so how does he know if his belief is true? His belief fails to pass the very test that he claims everything must fall subject to. 

I appreciated Allen's honesty with me. He didn't try to hide behind his views, but admitted the logical insanity of empericism. We ended up talking for a few minutes after the interview and he was very interested in what we were doing.