An artist, an architect, and an engineer were discussing whether it was better to have a wife or a mistress.
The architect said that it was better to have a wife, because you could build the relationship on a firm foundation.
The artist said that no, it was better to have a mistress, because the freedom allowed endless variations.
The engineer said that it was best to have both a wife and a mistress, because the wife would think he was with the mistress, the mistress would think he was with the wife, and he could go to the office and get some work done!