Epictetus' ethical theory revolves around a rational approach to those things within our power, and an indifference to those beyond our power. According to Epictetus, of those things within our power is our attitude, our reason, our "Faculty of Will". It is the faculty of Will that supercedes and commands all other faculties, and therein can true virtue or lack of virtue be found. If the faculty of will is righteous, then the person acts righteously; but if the faculty of will is corrupted, then the person will be corrupt. Further, it is the faculty of will which will determine the person's extent of happiness or unhappiness.
By Epictetus' logic, happiness or unhappiness is dependent upon our ability to acknowledge those things within and beyond our control. In order to achieve happiness, we must learn to focus our faculties and desires on that which is within our control and learn to dismiss that which is beyond our control. Once we have become conscious of those things which we cannot control, we can learn to embrace or at least be apathetic to any misfortune we may encounter. We can not, should not, grieve those misfortunes which we could not have avoided. Epictetus' view on misfortune was that it is relative to how we manage our desires, he said "What hurts this man is not this occurrence itself, for another man might not be hurt by it;-but the view he choose to take of it."
Spinoza had an interesting theory: that good and evil are not exactly objective concepts. Rather, they are our own subjective interpretations of the objective universe. According to him, they are the result of our understanding or misunderstanding of the divine order set forth by God. The logic in this case is this: God is perfect, God created the universe, therefore the universe is perfect. If the universe is perfect, there cannot be evil, only good. If we think that something is evil, it is because we have failed to comprehend the intricacies of God's universe.
Spinoza also argued that while the individual has certain limitations, they still possess the power to maximize those limitations and pursue a higher level of perfection. In this, we should all strive to attain the "knowledge of the union existing between the mind and the whole of nature". (107) This idea places responsibility on the individual to pursue higher and higher levels of good. Spinoza also puts a responsibility on the individual to help others in their quests for happiness, as doing so will also increase our level of content.
Both Epictetus and Spinoza agreed that our levels of happiness are contingent upon how we place our efforts and what we go about seeking in our lives. They favored pursuing greater things than riches and pleasure, what Spinoza called "the love of what is perishable". And they both agreed that to focus on thing so inconsequential only leads to ultimate unhappiness.
They both acknowledged the limitations of the individual, the fact that there are things beyond a person's control. But Spinoza placed more accountability on the individual then Epictetus did, as he argued that while we indeed have certain limitations that should not keep us from pursuing the absolute maximum of what is within our power.