III. Follow Nature. Define the Goal.

Seneca frames the central Stoic principle: live in accordance with nature.

Do not seek something that merely looks good. Seek something that is good all the way through, in the parts that are hidden as much as the parts that are seen.

My method, the Stoic method, is this: follow nature. Do not stray from it. Let reason study it and be advised by it.

A happy life is one that is in agreement with its own nature. What does this mean in practice?

It means a mind that is sound and stays sound. It means a mind that is bold and strong, able to endure hardship with genuine courage. It means a mind that is careful about the body and its needs, but not obsessively so. It means a mind that values the things that make life pleasant without overvaluing any of them. A mind that can enjoy what Fortune gives without being enslaved by it.

When you have done this, when you have cleared out the things that either excite you in the wrong direction or alarm you without reason, something replaces them: an immense and unchangeable joy. Peace. Calm. Greatness of mind. Genuine kindness toward others. Savageness, in any form, is always a sign of weakness.