But let us proclaim at once, that in regard to moral action, as in regard to health, no exact rules can be laid down.

Amidst perpetual variability, each agent must in the last resort be guided by the circumstances of the case.

Still, however, something may be done to help him.

Here Aristotle proceeds to introduce the famous doctrine of the MEAN.

We may err, as regards health, both by too much and by too little of exercise, food, or drink.