David Hume held the belief that ethics couldn’t be derived from reason but only from sentiment. Basically, morality is founded on non-rational emotional responses to experience. Hume thought of reason like a dog tied to a cart going wherever passion/desire would take it and doing so quite willingly.
Stoicism’s views are similar to Hume’s in the early stages of human development; for example, young children are motivated by the sentiment of self-love. However, when humans grow older they develop bonding relationships with people around them and eventually their rational faculties develop and they extend their self-love to love of others. First they develop love for their family, then their friends, then their community, then eventually for humanity.
The difference between Hume and the Stoics is that the Stoics believe that as you mature, you’ll eventually overcome sentimental morality. How does this come about? Well, it has to do with taking a look in the mirror and getting to know ourselves. Once we know ourselves we realize that our emotions are inflamed or defused by our cognitive/rational beliefs about the world.
Hume would say that our moral judgment comes from emotions/desires that are essentially beyond our control. But the Stoics believed that our emotions/desires were based on rational judgments that are within our control. In fact, the Stoics were clever enough to distinguish proto-passions from passions. Proto-passions are the knee-jerk feelings you get instantly from stimuli but passions come about from how you reflectively/actively decide to feel about the initial stimuli in the long-run.
Stoicism is actually quite radical because it essentially says that all of your desires or aversions to the external events or things in the world are based on cognitive/rational values you hold about those events or things. If you strongly desire ice cream, it’s because you believe ice cream to be good. If you hate ice cream, it’s because you believe ice cream to be bad. The Stoics were quite clever in how they dealt with desires/aversions because they replaced desires/aversions with preferences or dis-preferences because we should view the externals in our life as indifferent in light of our rational/cognitive moral judgment. The only true thing we should desire is virtue which is the true good, so everything else external is indifferent.
So Stoicism agrees with Hume in the early development of human beings but as reason develops in human beings, it grows and contributes more to passion than passion contributes to it. Stoicism, as a philosophy, amazingly kicks reason into high gear and allows us to really hone in on our passions, whether negative or positive, and learn how to manipulate them with reason. It’s not that reason is abstract/universal in a Kantian sense, reason is actually very concrete/contextual and interacts very strongly with the passions/desires and every value-laden belief we hold.
Hume is good for helping us think about our sentiments such that we wonder if our reason is more based on sentiments than our sentiments are based on reason. However, the Stoics are essentially right that reason prevails in our life. Well, reason prevails in our life if we allow ourselves to mature.