In the Preface to the original edition of his book, Napoleon Hill introduces a money-making secret that has led to the fortunes of over 500 wealthy individuals, a secret conveyed to him by renowned industrialist Andrew Carnegie over 20 years earlier.

Since Carnegie believed this secret should be taught in schools and colleges, it has been tested by thousands of people from various backgrounds. Carnegie’s dissatisfaction with traditional education led him to promote this secret with the potential to revolutionize education. However, education is irrelevant to the secret’s effectiveness.

Charles M. Schwab used the secret in forming US Steel; for him, this formula was worth around $600 million. Even before 20 years of practical testing, the secret was passed on to over 100,000 individuals, some of whom made fortunes, while others found success in creating harmony in their homes. Hill’s own son discovered and applied the secret during his college years, leading to immediate success in a well-paying job—a personal anecdote that Hill argues should dismiss any skepticism about the promises made in the book.

The secret has also had historical applications, such as its use by President Woodrow Wilson during World War I, and its inspiration for Manuel L.