Double-dealing
Anyone who displays a capacity for double-dealing must forever be suspected of being capable of displaying it again.
Not in a duel yet
Source: fiction-quotations.com
More from Foundation's Edge
The observer influences the events he observes by the mere act of observing them or by being there to observe them.
The advance of civilization is nothing but an exercise in the limiting of privacy.
A person who expects the completely sophisticated and who guards against it is quite apt never to think of the primitive.