Definition
The soft-sell is indirect persuasion: instead of pressing a case, it hides the pitch inside entertainment, charm, and good feeling. Greene devotes an appendix to it, contrasting it with the hard-sell — the blunt, obvious demand that puts a target on guard.
The soft-sell never seems to be selling. It amuses, flatters, or moves you, and lets you arrive at the desired conclusion as if it were your own.
Why it matters
How it works
The soft-sell substitutes mood for argument. It surrounds the real proposition with things the target enjoys — wit, beauty, flattery, a good story — so that the warm feeling generated by the wrapping transfers to the proposition inside it. Crucially, the persuader appears not to care whether you agree, which removes the pressure that would otherwise prompt scrutiny.
This is the logic of most modern advertising and of charming courtship alike: the sale is real, but it is staged as a pleasure rather than a demand.