A physicist, an accountant and a lawyer are all standing around at a party discussing if it's better to have a wife or a girlfriend.

The accountant says, "A girlfriend! No commitments, no hassles. When you get tired, you just move on."

The lawyer says, "One needs a wife. That way you have a representative; an extension of yourself at important gatherings with influential people."

The physicist says, "You're both wrong. You need a wife and a girlfriend. That way the wife thinks you're with the girlfriend, the girlfriend thinks you're with the wife and all the while you're at the lab doing research!"