Full Idea
Vague concepts are boundaryless, ...and the manifestations are an unwillingness to draw any such boundaries, the impossibility of identifying such boundaries, and needlessness and even disutility of such boundaries.
Gist of Idea
If concepts are vague, people avoid boundaries, can't spot them, and don't want them
Source
Mark Sainsbury (Concepts without Boundaries [1990], §5)
Book Reference
'Vagueness: a Reader', ed/tr. Keefe,R /Smith,P [MIT 1999], p.257
A Reaction
People have a very fine-tuned notion of whether the sharp boundary of a concept is worth discussing. The interesting exception are legal people, who are often forced to find precision where everyone else hates it. Who deserves to inherit the big house?