The thumb alone.

' I have a bookcase filled with surgical textbooks that describe operations people have devised for the injured hand: different ways to rearrange the tendons, muscles and joints, ways to replace sections of bones and mechanical joints - thousands of surgical procedures. But i know of no procedure that succeeds in improving a normal hand.... After operating on thousands of hands, I must agree with Isaac Newton, "In the absence of any other proof, the thumb alone would convince me of God's existance." ' - Paul Brand