Epictetus doesn’t have any known writings. His most well-known pupil, Arrian of Nicomedia, compiled the philosopher’s teachings in the four-volume work, Discourses. Moreover, Arrian wrote an abridged version of the Discourses, in a work titled Enchiridion, which stands for 'handbook' in Greek.

The key concepts that you will find in Epictetus teachings - mainly from Discourses and Enchiridion - are the following:

#1 Self-knowledge and Rationality

The core of Epictetus’s philosophy is the exploration of what it means to be a rational human being. Rationality means that you possess the ability to evaluate the content of your impressions to determine whether they are true or false. The idea of assent is critical for this process. In essence, we readily assent to (or agree to) a view that is in accordance with our own. However, if we spot any contradictions, we will and should reject one of the two views to get closer to the truth. For Epictetus, the most basic attribute of a human being is his inability to accept as true something that he views as false, and his aversion to deceit.

#2 The Importance of God

Apart from human rationality, Epictetus firmly believed in the rationality of the universe. The orderliness of the universe is maintained by Zeus, who the philosopher often refers to as “the god”. Despite being a supreme entity though, he is not an incomprehensible being. He is rational and possesses the same intentions as humans, and so with enough effort, we can understand him. The god’s attitude towards humans is that of benevolence.

#3 The Accountability of Our Actions

In Epictetus’s philosophy, you will find a distinction between the things in our power and those outside of it. Our ability to make choices is the one that makes us accountable for our actions and states. Freedom is an inseparable characteristic of any human being, and the ability to decide on our own accord should not be influenced by external compulsions.

Prohairesis or volition, which is the capacity for choice, makes the real individual. Every human’s convictions, attitudes, intentions, and actions are determined by his impressions of things and they belong in his prohairesis. These come in contrast to the external factors, such as the appearance of the body, the possessions, the successes and failures, the reputation in the world, and the relationships with other people.

#4 Our Emotional Disposition

The evaluation of the external factors (mentioned in the previous paragraph) can bring inner happiness and peace to an individual but should not be relied upon as once again, they are external. Negative feelings, such as fear, envy, and desire, derive from the notion that happiness depends on external elements. Both human feelings and behaviour are the result of what feels right to us. With self-examination and revaluation of our judgements, we will correct our feelings. Emotions like anger and betrayal derive from the behaviour of other people. Therefore, they are part of the external elements, and so, they are of no consequence to the individual.

#5 Achieving Autonomy

A human being must always strive for the correction of his views, which comes through self-examination. This ability to achieve autonomy is a part of human nature, as it stems from the reasoning faculty. When the individual learns to use his reasoning faculty, he can align his views with truth over time.

#6 Our Relationship with Those Around Us

When it comes to the people around us, Epictetus uses the words aidos (modesty) and philanthropia (love of humanity). The first term refers to the awareness of how others perceive you, as well as a willingness to correct unacceptable behaviour. The second term refers to the willingness to make yourself useful to others. The best expression of our love of humanity is to help others develop their rational nature.

 “No man is free who is not master of himself.”

“It is impossible for a man to learn what he thinks he already knows.”

“No thing great is created suddenly, any more than a bunch of grapes or a fig. If you tell me that you desire a fig, I answer you that there must be time. Let it first blossom, then bear fruit, then ripen.”

“Some things are in our control and others not. Things in our control are opinion, pursuit, desire, aversion, and, in a word, whatever are our own actions. Things not in our control are body, property, reputation, command, and, in one word, whatever are not our own actions.”

“Everything has two handles, the one by which it may be carried, the other by which it cannot. If your brother acts unjustly, don't lay hold on the action by the handle of his injustice, for by that it cannot be carried; but by the opposite, that he is your brother, that he was brought up with you; and thus you will lay hold on it, as it is to be carried.”