Although tact is a virtue, it is very closely allied to certain vices; the line between tact and hypocrisy is a very narrow one. I think the distinction comes in the motive: when it is kindliness that makes us wish to please, our tact is the right sort; when it is fear of offending, or desire to obtain some advantage by flattery, our tact is apt to be of a less amiable kind.

Mortals and Others: American Essays, 1931-1935 (1975)