It’s kind of an axiom why virtue is the only good for any Stoic. There’s not a perfect proof for why virtue is the chief good. You usually bite the bullet when you commit to any particular universal ethical theory. With Epicureanism, the chief good is pleasure. In utilitarianism, it usually means maximizing the everyone’s preferences or happiness. In Kantian deontology, it means not violating the categorical imperative.
But why choose virtue as the only good? Well, there are a plethora of reasons to do so. But first let’s say why you wouldn’t choose other ethical theories. Utilitarianism and Kantian deontology imply all sorts of ethical decisions that we might not be comfortable making. Utilitarianism is often thought of as as easily calculating the best decision for the most but it’s not always practical to know what’s the best for the most or even possible to know what’s the best for the most. Could utilitarianism condone slavery if slaves are unhappy or not having their preferences met but everyone who benefits from slavery are very happy or are definitely having their preferences met? That’s just one sort of problem with utilitarianism. The problems with morality in the name of utility can’t even be summed up in a single book while some have tried.
What about Kantian deontology? Immanuel Kant actually tried to sell his Metaphysics of Morals as rational foundation of morality that would actually be inline with our common sense. But is it common sense to have to tell the truth always even if it means you can never lie even if it’s to selflessly help another soul? That doesn’t strike anyone as common sense. Also, there are many times in our life where it seems sensible to do the utilitarian thing over the dignity of one individual. How many of us would pull the lever to save 5 lives over 1 life from a murderous Trolley? Probably a significant amount.
And what about making pleasure as the chief good? This seems sensible enough at first. But most people know you should follow pleasure and avoid point within limits. Limits of what? Usually within certain moral guidelines? So then pleasure isn’t the source of the good. Pleasure is actually being limited by something people view to be a higher good than pleasure itself. But we certainly want to allow for pleasure but only within certain constraints. The Epicureans attempted this project but it’s not certain they ever really succeeded because even though they managed to practice virtue, they still did not set it up as the chief good but as a way to not feel guilty when one has erred morally. Feeling guilty caused displeasure, so it’s best not to err morally. But why feel guilty in the first place if one has erred morally or contradicted virtue if virtue isn’t the chief source of the good? It really doesn’t seem to add up.
The Stoics didn’t actually care about feeling guilty if one had erred ethically. In fact, they’d really rather have you just learn from your mistakes rather than feel guilty about them. They knew that people make mistakes all the time, whether attempting to live the good life or being mistaken about what the good life was. There’s a lot of humility in Stoicism. We all make mistakes, so let’s try to fix them and then move on. No sense living in guilt or remorse. Sure, we can feel a little remorseful at first but no sense in grieving over our prior faults.
What’s more is Stoicism makes plenty of room for pleasure. It allows for pleasure, wealth, health, education, reputation, and many other preferred qualities in life we’d like to pursue so long as they don’t contradict the pursuit of the chief good virtue. Since most of these things don’t all the time contradict virtue, then pursuing virtue as the chief good is going to make for a pretty normal life. In fact, pursuing virtue for its own sake won’t make you stand dramatically out from the crowd of people you surround yourself in your daily life. People may wonder what makes you seem a little different than them though and they may want to emulate your behavior but that’s about it.
Virtue is also a pretty morally popular idea when you get people to thinking about what it is and what it entails. Most people, when you get them to think about it, would say that the soldier who jumps on the grenade to save the lives of other soldiers did something truly remarkably good. Virtuous in fact. Most people would also say that the person who risks their life drowning to save two other kids from drowning did something truly noble. It’s because people have this moral sense in their minds that seems to confirm the importance of virtue. That’s not to say that everyone is right about everything all of the time. But when you get people to think about what’s truly important, they’ll usually think someone doing something virtuous rather than something expedient is the right course of action.
Why would people have this moral sense? Perhaps it has to do with Hierocles’s Circles. Hierocles was an ancient Stoic who presumed that all humans began their infancy in self-love. And then as they grew and matured their self-love began to point outward towards their siblings and parents. And then as they grew older they loved their friends. And then they grew to love their community, and then love their society, and then finally humanity. It’s true that not everyone matures fully or matures the same. But there seems to be a general trend in humanity to go from self-love in infancy to love of everyone or philanthropy in adulthood.
What does this development of philanthropy have to do with virtue? Well one of the main virtues of the four cardinal virtues is justice. Justice has to do with fair dealings, equitability, and compassion. The Stoics knew this. They knew virtue was just an extension of love into the realm of universal love or justice. And they knew that temperance, courage, and wisdom all assisted in this universal love.
So this is why it’s worth biting the bullet for the axiom that virtue is the only good. There’s not a lot to lose like you do in all the other plethora of life philosophies out there and there’s plenty of things to gain from one philosophy: Stoicism.