 As Massey (1975) reminds us, the fact that there are other arguments with the form \(\refp{propform}\) that have true premises and a false conclusion does not show that \(\refp{firefighter}\) is invalid (or even that it is “formally” invalid). The Demarcater will insist that a genuine counterexample to the formal validity of \(\refp{firefighter}\) would have to exhibit the full logical structure of \(\refp{firefighter}\), which is not \(\refp{propform}\) but \(\refp{quantform}\).  Thus the Demarcater’s use of counterexamples to demonstrate the formal invalidity of arguments presupposes a principled way of discerning the full logical structure of an argument, and hence of distinguishing logical constants from nonlogical  constants.[26]