To put it in programming terms, this: if product.may_have_trace('peanuts') add_warning() is generally better than if product.may_have_trace('peanut

To put it in programming terms, this: if product.may_have_trace('peanuts') add_warning() is generally better than if product.may_have_trace('peanuts') if ! product.name_obviously_implies('peanuts') add_warning() Eliminating a special cast at the cost of a redundant warning on some products is probably a new win.