Full Idea
Convention, to exist at all, must have a basis in something that is not conventional; conventions, to work, need something nonconventional to build upon and shape.
Gist of Idea
Conventions can only work if they are based on something non-conventional
Source
Robert Fogelin (Walking the Tightrope of Reason [2003], Ch.3)
Book Reference
Fogelin,Robert: 'Walking the Tightrope of Reason' [OUP 2004], p.75
A Reaction
Fogelin attributes his point to Hume. I agree entirely. No convention could ever possibly catch on in a society unless there were some point to it. If you can't see a point to a convention (like wearing ties) then start looking, because it's there.