But let it be understood, before we go on, that all reasoning on matters of practice must be in outline merely, and not scientifically exact: for, as we said at starting, the kind of reasoning to be demanded varies with the subject in hand; and in practical matters and questions of expediency there are no invariable laws, any more than in questions of health.

And if our general conclusions are thus inexact, still more inexact is all reasoning about particular cases; for these fall under no system of scientifically established rules or traditional maxims, but the agent must always consider for himself what the special occasion requires, just as in medicine or navigation.

But though this is the case we must try to render what help we can.