Whether Bentham was right, however, depends on whether the existing rule, true to the very idea of a rule, is entrenched firmly enough to resist or tolerate at least some suboptimal results. … If common-law rules will be modified when they produce very bad or substantially suboptimal results, but not when they produce only somewhat or slightly suboptimal results, then the rules will operate as rules do, even if they allow at times some number of somewhat or slightly bad or moderately suboptimal results.

Unknown, Frederick Schauer - Thinkin…, loc. 223