Definition
The Carnegie secret is the never-explicitly-named principle that Think and Grow Rich claims runs through every topic. The book attributes the idea to the industrialist Andrew Carnegie and presents it as a single insight that the reader must recognize for themselves, arguing that a truth grasped through one's own effort takes hold more firmly than one handed over directly.
In substance, the secret is the conviction that everything a person achieves begins as a definite idea, charged with desire and belief, and that the mind is the workshop where success is first constructed before it appears in the world.
Why it matters
How it works
The book never spells the secret out in a sentence; instead it surfaces in fragments across the topics on desire, faith, autosuggestion, and persistence. The intended experience is one of gradual recognition: the reader who is genuinely ready notices the principle emerging from the pattern of the text. The mechanism is partly literary and partly psychological — by making the reader do the work of discovery, the book aims to convert the principle from information into personal conviction.