Philosophers have debated for millennia the nature of ethics. Is it arbitrary? Or are there universal moral laws that we can apprehend through reason? Neither, say the Stoics. Theirs is a thoroughly naturalistic philosophy.

Desires have to be reined in, fear to be suppressed, proper actions to be arranged, debts to be paid; we therefore include self-restraint, bravery, prudence, and justice among the virtues – assigning to each quality its special function.

There are, as you know, vices which are next-door to virtues. Carelessness looks like ease, and rashness like bravery.

No doubt you have seen dogs playing with, and fawning before, each other, and thought, ‘Nothing could be friendlier.’ But just throw some meat in the middle, and then you’ll know what friendship amounts to.

The Stoics understood what bodily health is, and from that they deduced the existence of a certain mental health also. They knew about bodily strength, and from that they inferred the existence of mental sturdiness.

The Stoics regard nothing as good which can be put to wrong use by any person. And we can all see for ourselves to what wrong uses many people put their riches, their high position, or their physical powers.

Externals — such as money, possessions, and the like — are how we exercise our virtue, which cannot be expressed in a vacuum. And one of the four cardinal virtues is temperance.

He who has much, desires more – a proof that he has not yet acquired enough; but he who has enough has attained that which never fell to the rich man’s lot – a stopping-point.

In order to live a meaningful life (ethics) we need to reason well about things (logic), and we need to have a good grasp of how the world works (science). How are your logic and science, then?

We take a lot of things for granted, when life is going well for us. But — fools that we are — we really appreciate what we had only once we’ve lost it. That's why the Stoics devised a series of exercises in mild self-deprivation.