In Our Power (eph hêmin)
For the Stoics, for a thing to be 'in our power' (eph hêmin), it has to be completely in our control. Stated simply, the only things absolutely in our control are the capacities of our minds. Specifically, what is in our power is the capacity to choose, to exercise our moral wills. In our power are our opinions (beliefs, judgments), impulses (intentions to act), desires, and aversions.
Everything else, being external to our wills, or moral characters, is 'not in our power'.
Keith Seddon, "What is in our power":
"To maintain our prohairesis (moral character) in the proper condition
the successful accomplishment of this being necessary and sufficient for
eudaimonia (happiness) we must understand what is eph hêmin
(in our power or up to us; see Discourses 1.22.916). If we do
not do this, our prohairesis will remain in a faulty condition,
for we will remain convinced that things such as wealth and status are good when
they are really indifferent, troubled by frustrations and anxieties, subject to
disturbing emotions we do not want and cannot control, all of which make life
unpleasant and unrewarding, sometimes overwhelmingly so."
Things 'in our power' and things 'not in our power' represent the two components of Fate: internal and external causation.
"A human agent is not like a billiard ball, which if struck must
move off in a certain direction at a certain speed. When struck by an
impression, the agent can decide what to do, can decide to assent to it, and
can decide what to do next. But just as the cylinders roundness had antecedent
causes so that its being like that fitted in to the overall causal nexus of
fate, so too does the agents nature have antecedent causes, these being the
agents upbringing, attending the classes of a Stoic teacher, and what have
you. So again, the theory of causal determinism is unviolated — and it
is up to the agent, and in their power to assent to impressions and to act
as they see fit. If this has all been argued correctly, Chrysippus can
have his cake and eat it: that is, causal determinism is true, and
agents can exercise their free will" (Seddon, 1999).
Epictetus, Discourses 1.1.7-12
"As then it was fit to be so, that which is best of all and supreme over all is the only thing which the gods have placed in our power, the right use of appearances; but all other things they have not placed in our power. Was it because they did not choose? I indeed think that, if they had been able, they would have put these other things also in our power, but they certainly could not. For as we exist on the earth, and are bound to such a body and to such companions, how was it possible for us not to be hindered as to these things by externals"? (trans. George Long)
Epictetus, Discourses 4.1.128-31
"The unconstrained person, who has access to the things that he wants, is free. Whereas he who can be constrained or necessitated or impeded or thrown into anything against his will is a slave.
Who is unconstrained?
The person who seeks after nothing that is not his own.
What are the things not one's own?
Everything that is not up to us to have or not to have, or to have thus and so qualified, or thus and so disposed. Therefore the body is not one's own, nor its members, nor property. If, then, you attach yourself to any of these things as if it were your own, you will pay the appropriate penalty of one who seeks things that are not one's own. The road that leads to freedom, and the only release from enslavement, is to be able to say wholeheartedly: Lead me, Zeus and you, Fate, wherever you have ordained for me" (trans. Long, 2002, pg. 221).
Epictetus, Handbook 1.
Of things some are in our power, and others are not. In our power are opinion, movement toward a thing, desire, aversion (turning from a thing); and in a word, whatever are our own acts: not in our power are the body, property, reputation, offices (magisterial power), and in a word, whatever are not our own acts. And the things in our power are by nature free, not subject to restraint nor hindrance: but the things not in our power are weak, slavish, subject to restraint, in the control of others. Remember then that if you think the things which are by nature slavish to be free, and the things which are in the power of others to be your own, you will be hindered, you will lament, you will be disturbed, you will blame both gods and men: but 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 (against your will), no man will harm you, you will have no enemy, for you will not suffer any harm.
If then you desire (aim at) such great things, remember that you must not (attempt to) lay hold of them with a small effort; but you must leave alone some things entirely, and postpone others for the present. But if you wish these things also (such great things), and power (office) and wealth, perhaps you will not gain even these very things (power and wealth) because you aim also at those former things (such great things): certainly you will fail in those things through which alone happiness and freedom are secured. Straightway then practice saying to every harsh appearance, You are an appearance, and in no manner what you appear to be. Then examine it by the rules which you possess, and by this first and chiefly, whether it relates to the things which are in our power or to the things which are not in our power: and if it relates to anything which is not in our power, be ready to say, that it does not concern you (trans. George Long).
'in our power' (eph hêmin). See Discourses 1.1, 1.6.40, 1.12.32-4, 1.18.12, 1.22.9-10, 1.29.8, 2.1.12, 2.2.6, 2.5.4/8, 2.13.1-2/10-11, 2.19.32, 3.3.10, 3.24.1-3/22-3, 3.26.34, 4.1.65-83/100/128-31, 4.4.15, 4.7.8-10, 4.10.8/28; Handbook 1.1-2/5, 2.1-2, 14.1-2, 18, 19.1-2, 24.1-2, 25.1, 31.2, 32.1-2, 48.3 (referrences, Seddon, forthcoming).
Long, A. A., Sedley, D. N. (1987). The Hellenistic
Philosophers: vol. 1. translations of the principle
sources with philosophical commentary. Cambridge,
England: Cambridge University Press.
Long, A. A. (2002). Epictetus: A Stoic and Socratic Guide to Life. New York: Oxford University Press.
Seddon, Keith (1999). Stoics on fate and determinism.
Seddon, Keith (2001). "What is in our power." Epictetus [Internet Encyclopedia of Philosophy]