When I began dabbling in Stoic philosophy it was a quick relief for my anxiety, regret, and anger. Before investigating Stoicism, I moved from philosophy to philosophy as I had done since high school. I knew of Stoicism since first getting into philosophy, but I never understood how virtue led to happiness. I found it hard to believe that virtue is sufficient for happiness, so I never investigated Stoicism further. I also never researched Stoicism because I had not heard of Epictetus or Seneca. I heard of Marcus Aurelius, but I never made the connection that he was a Stoic, I just figured he was well read in a variety of schools, but I never knew he was partial to Stoicism. When I figured out that Stoicism had a super coherent set of beliefs and a robust philosophical basis, I fell in love with it. What got me into Stoicism initially was the therapeutic value.
I feel like a significant amount of people stop at the Stoic therapy when they read texts from Marcus Aurelius, Epictetus, and Seneca. They do not go further than the therapy part. But after I felt joy learning about the Stoic techniques of memento mori, premeditatio malorum, view from above, endure and renounce, dichotomy of control, and amor fati, I learned something more powerful than mere coping techniques. I learned that virtue is the absolute center of Stoicism. In fact, Stoics believe that virtue is the sole good. There is literally nothing good other than virtue, excellence, a noble soul, a wise person, the Sage.
Virtue is the only good and it is difficult to understand it initially if you have not practiced the four virtues or spent time understanding how the wise person can appropriately judge all externals as indifferents (which means externals have no moral value good/bad). Virtue is the starting point of Stoicism and virtue gives the dichotomy of control context. Your character (judgment/will) is the only thing that you can truly control and so it is the only thing that can be either good (virtuous) or bad (vicious). A good character should lead to a better life or a eudaimonic life (which is a joyful life that is internal and caused by an ethical purpose). It is important to note that you cannot be virtuous if you do not focus on all the four virtues: justice, fortitude, wisdom, and temperance. I will not go into detail about fortitude, wisdom, and temperance for now, but I will focus on justice.
Justice is why Stoics have a duty to others. Justice means you must be kind and fair to others. The Stoics did not mean that justice was tough love or retributive. They meant for it to be kind and fair. You cannot have fairness without kindness, and you cannot have kindness without fairness. Stoicism does not separate mercy and justice because justice is a kind of mercy. The merciful are just. It is important that when we judge people as vicious, we realize that they are suffering from pathos. Pathos literally means suffering, and it manifests in anger, hate, jealousy, fear, and any kind of emotion that results from judging any external as either good or bad. The bad person suffers and when they harm others it is like their suffering is spilling over onto others. So, since justice is kindness and fairness, it means that we have a duty to others. We must know people as well as we can and help them as best as we can. Sometimes doing what is right for someone is to leave them alone. Sometimes practicing the virtue of justice is helping someone when they genuinely ask for help.
The important part of being a Stoic is that justice does not conflict with one’s eudaimonic happiness. It does not conflict with a joyful soul. Joy should be the result of doing what is rationally and ethically correct for the situation. The Stoics did not distinguish selfishness and altruism. Selfishness and altruism were intricately tied together. So, the best thing that you can do for yourself is to help others. But you should not help people in order to feel good because that is not going to work. You should help people because it is the right thing to do and that will make you a better person and so you will experience authentic joy.