None of them can go beyond experience, or establish any principles which are not founded on that authority.

Moral philosophy has, indeed, this peculiar disadvantage, which is not found in natural, that in collecting its experiments, it cannot make them purposely, with premeditation, and after such a manner as to satisfy itself concerning every particular difficulty which may arise.

When I am at a loss to know the effects of one body upon another in any situation, I need only put them in that situation, and observe what results from it.

But should I endeavour to clear up in the same manner any[15] doubt in moral philosophy, by placing myself in the same case with that which I consider, 'tis evident this reflection and premeditation would so disturb the operation of my natural principles, as must render it impossible to form any just conclusion from the phenomenon.

We must, therefore, glean up our experiments in this science from a cautious observation of human life, and take them as they appear in the common course of the world, by men's behaviour in company, in affairs, and in their pleasures.