Describing an emotion

How can a man with sight
Be so very blind
How can a man so smart
Search his brain for an answer he'll never find

How can a man who hears
Be deaf to words often spoken
How can a man who's whole
Often feel completely broken

How can a man who feels
Reach for something he can't touch
How can a man who's found
Find himself lost so much

How can a man taste
But only taste a poison that can kill
How can a man smell
But only her scent makes him feel real

How can a mans life be driven
By only one emotion
It's not to hard to figure out
I'm sure you have a notion...