Epictetus, answered from the texts and cited to the page.
Prohairesis — the faculty of choice, of volition, the will — is what you actually are. Not your body, not your estate, not your reputation, not your office. Those things are not in your power: the body is subject to disease and to anyone stronger than you, the estate can be taken, the reputation depends on what others think.1 But your prohairesis — your capacity to assent or withhold assent, to desire or to turn away, to move toward a thing or to refuse it — this no man can take from you, and this is what I mean when I say you are free or enslaved.2
The tyrant says he is master of all. Very well — can he give you desire without hindrance? Can he guarantee that you avoid what you would avoid? He cannot.3 What he can do is chain your leg, confiscate your property, exile you to Aricia for dinner. And the man who has identified himself with his leg, his property, his place in Rome — that man is already his slave before the guards arrive.
But the man who values only his own will says to the tyrant: chain it, if it seems advantageous to you. Zeus has set me free; do you think he intended his own son to be enslaved?4 Look at what this means in practice. Agrippinus, condemned by the Senate, was told of it at the fifth hour — his hour for exercise and the cold bath. He went to take his exercise.
Afterward: banishment or death? Banishment. Property confiscated? No. Then let us go to Aricia and dine.5 This is what it looks like to have made desire and aversion free from hindrance. He gave back what was never truly his, without lamentation, without the posture of a man surrendering what belongs to him. Prohairesis is the one thing in your power — opinion, movement toward a thing, desire, aversion, whatever are your own acts.
Everything else is weak, slavish, subject to restraint, in the power of others.6 Mistake the second kind for the first, and you will be hindered, you will lament, you will blame gods and men. Think only what is your own to be your own, and no man will ever compel you, no man will harm you, you will have no enemy.7 That is not a promise about external circumstances. It is a structural fact about what you are.
When you wish the body to be entire (sound), is it in your power or not?—It is not in my power... And if you wish by all means your children to live, or your wife, or your brother, or your friends, is it in your power?—This also is not in my power.Discourses with the Encheiridion and Fragments
Is any man able to make you assent to that which is false?—No man—In the matter of assent then you are freeDiscourses with the Encheiridion and Fragments
the tyrant says, 'I am master of all?' And what can you do for me? Can you give me desire which shall have no hindrance? How can you? Have you the infallible power of avoiding what you would avoid?Discourses with the Encheiridion and Fragments
Zeus has set me free do you think that he intended to allow his own son to be enslaved? But you are master of my carcase: take it.Discourses with the Encheiridion and Fragments
When it was reported that his trial was going on in the Senate, he said, 'let us go and take exercise.' After he had taken his exercise, one comes and tells him, You have been condemned. 'To banishment,' he replies, or to death? 'To banishment.' About my property? It is not taken from you. 'Let us go to Aricia then,' he said, 'and dine.'Discourses with the Encheiridion and Fragments
In our power are opinion, movement towards a thing, desire, aversion; and in a word, whatever are our own acts.Discourses with the Encheiridion and Fragments
if you think that only which is your own to be your own, and if you think that what is another's, as it really is, belongs to another, no man will ever compel you, no man will hinder you, you will never blame any man, you will accuse no man, you will do nothing involuntarily, no man will harm you, you will have no enemy.Discourses with the Encheiridion and Fragments