Letters to His Son is not a treatise but a long private correspondence: the Earl of Chesterfield writing repeatedly to his illegitimate son, Philip Stanhope, as the young man travels and studies across Europe in the 1740s and after. Each letter opens 'Dear Boy' and mixes affection, scrutiny, and instruction, aiming to fashion the son into an accomplished man of the world.
The father's project is candidly worldly. He wants his son to shine in the great and busy world of courts and statesmanship, and he treats almost every quality required for it as something that can be acquired by care, labor, and attention. Laziness, inattention, and indifference are named as the son's faults, and the letters return again and again to correcting them.
A central teaching is that manner matters as much as matter. Chesterfield warns that good sense spoken in bad words, an awkward air, or an ill-spelled letter will be laughed at or ignored. He elevates 'the graces' (pleasing speech, easy address, graceful motion) as the polish without which knowledge and merit fail to persuade, especially in public assemblies, courts, and negotiations.
Alongside polish he urges the study of human nature. The son is told to become a portrait painter of the inside of the heart and mind, discovering people's predominant passions and weaknesses. This is the true knowledge of the world, learned by traveling through it and observing it in courts and camps, where every kind of character is seen in action. Good-breeding, he adds, is local, so a sensible man flexibly conforms to the customs of wherever he is.
Underlying all of it is a discipline of attention and time. Chesterfield praises doing one thing at a time, banishing other objects from the mind, and taking care of the minutes so the hours take care of themselves. His counsel is at once practical and pointed, and modern readers also notice what he omits: warmth, principle, and depth of heart are largely subordinated to the goal of pleasing, succeeding, and never appearing ridiculous.