Stoic ethics rests on a claim that sounds extreme at first: virtue is the only true good, and vice the only true evil. Everything else, including health, wealth, reputation and even life itself, is neither good nor bad in the strict sense.

Why only virtue?

The Stoics reasoned roughly like this. Something truly good must always benefit its possessor and can never be used badly. Money can fund a hospital or a crime; health can serve a generous person or a cruel one; fame can come to fools. Only virtue, the excellence of a rational mind, is good in every circumstance, because it is precisely the skill of using everything else well. Socrates had suggested something similar in Plato's dialogues, and the Stoics saw themselves as his heirs.

It follows that virtue is sufficient for happiness. A good person who loses property, health or freedom has not lost what matters most. This is the source of Stoic resilience, and also of the main objections to it (Level 8).

The four cardinal virtues

Following a tradition going back to Plato, the Stoics named four main virtues:

• Wisdom (practical wisdom): knowing what is good, bad and neither, and how to act.
• Justice: giving others their due, including fairness, honesty and kindness, in a community of rational beings.
• Courage: knowing what is truly to be feared and what is not, and so enduring hardship rightly.
• Moderation (temperance, self-control): ordering desires so that they follow reason.

The Stoics held that the virtues are a unity: they are aspects of one well-ordered mind, so you cannot truly have one virtue without the others. A bold person without justice is not courageous but merely reckless or dangerous.

Indifferents: preferred and dispreferred

If health and wealth are not good, are they worthless? No. The Stoics called them indifferents, meaning they make no difference to whether a person is good or happy. But indifferents are not all equal. Some are preferred: good health, strength, wealth, good reputation, friends and family flourishing. Others are dispreferred: illness, poverty, disgrace, pain. It is natural and reasonable to choose the preferred ones, and to avoid the dispreferred, when you can do so without acting wrongly.

A useful way to put it: preferred indifferents have value for selection but are not part of goodness itself. Virtue is the skill of selecting among them well. A wise person will look after her health and earn a living, but she will not lie or betray a friend to gain either, and she will not consider her life ruined if she loses them.

Appropriate actions

The Stoics used the term kathēkonta, “appropriate actions” or “duties,” for acts that reason recommends given a person's nature and roles: caring for one's body, honoring parents, serving one's city. Ordinary people perform many appropriate actions. When done from a fully virtuous disposition, they become what the Stoics called right actions.

The sage

The ideal of perfect virtue was the sage, a rare ideal person who always judges and acts rightly. The Stoics admitted the sage is extremely rare, perhaps nonexistent. Everyone else is “making progress” (in Greek, prokoptōn, one who is progressing). They also held a striking view that all who fall short of virtue are equally not virtuous, as a person drowning one inch below the surface is drowning as surely as one far below. This sounded harsh to critics, but the Stoics paired it with a lifelong emphasis on steady improvement: the point of the image is that we should keep swimming upward, not that small gains are worthless.

Worked example: credit for a project

Lena and her colleague Omar spent months on a project that impressed the company's directors. In a meeting, a director assumes Lena did most of the work and hints that a promotion may follow. Omar is away that day. Lena could stay silent, gain the promotion and a higher salary, and perhaps no one would ever know. How would a Stoic reason?

First, sort the goods. The promotion, the salary and the directors' admiration are preferred indifferents. They are worth having, and it would be reasonable for Lena to seek them by fair means. But none of them is good in the strict sense. They cannot make her a better person, and she could live well without them.

Second, consider the virtues. Justice requires giving Omar his due. Courage means speaking up even if it costs her. Moderation means not letting her desire for advancement overrule her reason. Wisdom means seeing clearly that staying silent would trade the only true good, her own integrity, for an indifferent.

So Lena says: “Omar did at least half of this, and the analysis was mostly his.” She may lose the promotion, or the directors may respect her honesty and reward both of them. Either way, the Stoic would say she has kept the one thing that matters.

Notice what Stoicism does not say. It does not tell Lena that wanting a promotion is shameful, or that she should refuse one fairly earned. Preferred indifferents are meant to be selected, just never at the price of virtue. The theory turns a vague feeling that something would be wrong into a clear structure for deciding.