My success as a salesman depends on trust: Before I can close a sale with you, you have to trust me. But this requires me to act deliberately in a way that appears sincere. It’s not enough simply to be sincere and hope that you notice this; my best interests are served by actively cultivating this impression. And this kills true sincerity — now I’m self-consciously promoting an appearance.

“If sincerity is a natural and unforced conformity between avowals and actions, then it does not make sense to try to be sincere or to devise strategies for becoming more sincere, both of which require the deliberate attempt to achieve a state that cannot be brought about by calculation,” writes Monmouth College philosopher Guy Oakes. “Their self-consciousness — their knowledge of the circumstances of their role and the conditions required for its performance — rules out the possibility of sincerity. Sincerity produces insincerity.”

(Guy Oakes, “The Sales Process and the Paradoxes of Trust,” Journal of Business Ethics 9:8 [August 1990], 671-679.)