The Stoic experience consists in becoming sharply aware of the tragic situation of human beings, who are conditioned by fate. It would seem that we are not free at all, for it is not up to us to be beautiful, strong, healthy, or rich, to feel pleasure, or to escape suffering. All these things depend on causes which are external to us. A necessity which is inexorable and indifferent to our individual interest breaks our aspirations and our hopes; we are helpless and defenseless in the face of the accidents of life, the setbacks of fortune, illness, and death. Everything in our life escapes us. The result of this is that people are unhappy, because they passionately seek to acquire things which they cannot obtain and to flee evils which are inevitable.
There is one thing, and only one, which does depend on us and which nothing can tear away from us: the will to do good and to act in conformity with reason. There is thus a radical opposition between what depends on us and can therefore be either good or bad, since it is the object of our decision, and what depends not on us but on external causes and fate and which is therefore indifferent. The will to do good is an unbreachable fortress which everyone can construct within themselves. It is there that we can find freedom, independence, invulnerability, and that eminently Stoic value, coherence with ourselves.
Seneca summed up this attitude in the following saying: “Always want the same thing; always refuse the same thing. For the same thing can please people universally and constantly only if it is morally right.” Such self-coherence is the domain of reason. Rational discourse cannot but be self-coherent; and living according to reason means submitting to this demand for coherence. Zeno defined the Stoic choice of life as follows: “To live coherently – that is, according to a rule of life which is unique and harmonious. For those who live in incoherence are unhappy.”
To find a basis for this theory of “duties:’ the Stoics return to their fundamental intuition: that of the living being’s instinctive, original accord with itself, which expresses the deepest will of nature. Living beings have an innate tendency to preserve themselves and to repel that which threatens their integrity. When human reason appears, natural instinct becomes reflective, reasoned choice: something is chosen because it responds to the natural tendencies, such as the love of life and of children, or love for one’s fellow citizens, which is based on the instinct of sociability. To marry, to be active politically, to serve one’s country-all these actions are appropriate to human nature, and therefore have value. What characterizes “appropriate actions” is the fact that they partly depend on us, since they are actions which presuppose a moral intention, and partly do not depend on us, since their success hinges not our will alone but also on other people or on circumstances, external events, and ultimately Fate.
The Stoic always acts “under reserve” -but he does act, taking part in social and political life. This is another important point which separates him from the Epicureans, who in principle retire from everything that may cause worry.
Source: What is Ancient Philosophy?