Stoicism is a philosophy that was founded by the ancient Greek philosopher Zeno of Citium in the 3rd century BCE. It emphasizes the idea that individuals should focus on what they can control and accept the things they cannot control. According to the Stoics, living in accordance with reason and virtue is the key to living a good life, and emotions such as anger, fear, and sadness should be kept in check.

One of the central principles of Stoicism is that the only thing that a person can truly control is their own thoughts and actions. External events and circumstances are considered to be beyond an individual's control, and it is therefore pointless to worry about them. Instead, the Stoics believed that people should focus on living in accordance with reason and virtue, and strive to cultivate a calm and rational mind.

Another key aspect of Stoicism is the idea of "apathy," or the detachment from emotions. The Stoics believed that strong emotions can be detrimental to one's wellbeing, and that it is important to cultivate a sense of calm and detachment in order to live a good life. This does not mean that Stoics were emotionless or uncaring, but rather that they believed in maintaining control over one's emotions and not letting them get the better of them.

The Stoics also believed in living a simple and virtuous life, and that material possessions and external success are not necessary for happiness. They believed that living a virtuous life and acting in accordance with reason is what brings true happiness and fulfillment.

Overall, the Stoicism philosophy is centered around the idea that individuals have the ability to control their own thoughts and actions, and that living a virtuous life in accordance with reason is the key to living a good life. It emphasizes the importance of self-control, detachment from emotions, and living a simple and virtuous life.