A doctor, a lawyer and a mathematician were discussing the relative merits of
having a wife or a mistress.

The lawyer says, For sure a mistress is better. If you have a wife and want a
divorce, it causes all sorts of legal problems.

The doctor says, It is better to have a wife because the sense of security
lowers your stress and is good for your health.

The mathematician says, You are both wrong. It is best to have both so that
when the wife thinks you are with the mistress and the mistress thinks you are
with your wife – you can do some mathematics.