Full Idea
Categories as prototypes can be extended with modifiers (called 'hedges'), such as 'par excellence', 'strictly speaking', 'loosely speaking', 'technically', and 'in certain respects'.
Gist of Idea
Categories as prototypes can be qualified by a variety of verbal 'hedges'
Source
G Lakoff / M Johnson (Metaphors We Live By [1980], 19)
A Reaction
[They cite Lakoff 1975] These two are committed to the prototype view (which seems plausible to me), and this addition of hedges greatly strengthens that theory, which can otherwise sound implausibly rigid (e.g. the prototype human being).
Book Reference
Lakoff,G/Johnson,M: 'Metaphors We Live By' [Chicago 2003], p.123