Not a Tail

I ran across this article on gay marriage the other day, which I found quite interesting. Here's the first sentence:

Abraham Lincoln once asked how many legs a dog has if we call a tail a leg. The answer, he said, is four: calling a tail a leg does not make it so. We chuckle and move on.

It also had a line that I got quite a kick out of: "First, human beings have a powerful hankering to engage in sexual intercourse."