The system of Descartes... seemed to give a plausible reason for all those phenomena; and this reason seemed more just, as it is simple and intelligible to all capacities. But in philosophy, a student ought to doubt of the things he fancies he understands too easily, as much as of those he does not understand.
I read these words which are the sum of all moral philosophy, and which cut short all the disputes of the casuists: When in doubt if an action is good or bad, refrain.