In this third section, Emerson comments on the scholar's need for action, for physical labor. He rejects the notion that the scholar should not engage in practical action. Action, while secondary to thought, is still necessary: "Action is with the scholar subordinate, but it is essential." Furthermore, not to act — declining to put principle into practice — is cowardly. The transcendental concept of the world as an expression of ourselves makes action the natural duty of a thinking person.
Emerson observes the difference between recent actions and past actions. Over time, he says, a person's past deeds are transformed into thought, but recent acts are too entangled with present feelings to undergo this transformation. He compares "the recent act" to an insect larva, which eventually metamorphoses into a butterfly — symbolic of action becoming thought.
Finally, he praises labor as valuable in and of itself, for such action is the material creatively used by the scholar. An active person has a richer existence than a scholar who merely undergoes a second-hand existence through the words and thoughts of others. The ideal life has "undulation" — a rhythm that balances, or alternates, thought and action, labor and contemplation: "A great soul will be strong to live, as well as strong to think." This cycle creates a person's character that is far superior to the fame or the honor too easily expected by a mere display of higher learning.