ambitious arguments might threaten a local breakdown of rationality, a breakdown in some particular area. It might hold, for instance, that certain sceptical positions would preclude the possibility of the exercise of rationality in the practical domain. While such arguments may be expected to carry weight with some philosophers, a really doughty sceptic is liable to accept the threatened curtailment of rationality; he may, as Hume and those who follow him have done, accept the virtual exclusion of reason from the area of action. The threat, however, may be of a total breakdown of the possibility of the exercise of rationality; and here even the doughty sceptic might quail, on pain of losing his audience if he refuses to quail. 95