ABSTRACT
The method of doubt has a dual role in the working out of the Cartesian project. First, it filters out false beliefs; second, it abets the discovery of knowledge. It is chiefly in this second goal that Cartesian scepticism differs from other varieties of doubt: mere erroravoidance, though desirable, must be coupled with truth-finding. Not all truths, however, are of equal interest or importance; and it is an essential feature of the Cartesian method of doubt that it claims to lead us to truths which are peculiarly deep, fecund and powerful. In particular, under the pressure of the most extreme version of the sceptical hypothesis, we are forced to make explicit to ourselves the idea of a veracious God, the master concept which enables the sceptical hypothesis to be overcome. From the idea of God we are able to derive the general rule that all our clear and distinct perceptions are true; and equipped with that rule, we can proceed to extend the domain of what is known without exposing ourselves to the rise of error.
