As a result of Hill's studies via Carnegie's introductions, the Philosophy of Achievement was offered as a formula for rags-to-riches success by Hill and Carnegie, published initially in 1925 as a multi-volume study course called The Law of Success, later re-released in 1928 in an abridged version under the same title. The Achievement formula was detailed further and published in home-study courses, including the seventeen-volume "Mental Dynamite" series until 1941.
Hill later called his personal success teachings "The Philosophy of Achievement", and he considered freedom, democracy, capitalism, and harmony to be important contributing elements to this philosophy. Hill claimed throughout his writings that without these foundations upon which to build, successful personal achievements were not possible. He contrasted his philosophy with others' and thought that the Achievement Philosophy was superior. He felt that it was responsible for the success Americans enjoyed for the better part of two centuries. Negative emotions such as fear, selfishness, etc., had no part to play in his philosophy. Hill considered those emotions to be the source of failure for unsuccessful people.
The secret of achievement was tantalizingly offered to readers of Think and Grow Rich, but Hill felt readers would benefit most if they discovered it for themselves. Although most readers feel that he never explicitly identified this secret, he offers these words about 20 pages into the book: If you truly desire money so keenly that your desire is an obsession, you will have no difficulty in convincing yourself that you will acquire it. The object is to want money, and to be so determined to have it that you convince yourself that you will have it. . . You may as well know, right here, that you can never have riches in great quantities unless you work yourself into a white heat of desire for money, and actually believe you will possess it.
He presented the idea of a "Definite Major Purpose" as a challenge to his readers in order to make them ask themselves, "In what do I truly believe?" According to Hill, 98% of people had few or no firm beliefs, and this alone put true success firmly out of their reach.
One of Hill's most moving stories was about his own son, Blair. He tells how his son was an inspiration to him, because although Blair was born without ears, without any normal hearing organs at all, even though his doctor told Hill that his son would neither be able to hear nor speak, Blair grew up to be able to hear and speak almost normally. Hill tells how his son, in his last year of college, picked up the manuscript of chapter two of Think and Grow Rich, discovered Hill's secret for himself and went on to be an inspiration for hundreds and thousands of people who could not hear or speak.
From 1952 to 1962, Hill taught his Philosophy of Personal Achievement –
Lectures on "Science of Success" in association with W. Clement Stone. In 1960, Hill and Stone co-authored the book, Success Through A Positive Mental Attitude. Norman Vincent Peale stated "These two men [Hill and Stone] have the rare gift of inspiring and helping people...In fact, I owe them both a personal debt of gratitude for the helpful guidance I have received from their writings." 
Think and Grow Rich remains the top seller of Napoleon Hill's books – a perennial best-seller after 70 years (Business Week Magazine's Best-Seller List ranked Think and Grow Rich as the sixth best-selling paperback business book 70 years after it was first published). Think and Grow Rich is listed in John C. Maxwell's A Lifetime "Must Read" Books List. 
Hill's numerous books have sold millions of copies, showing that the secret of achievement is still highly sought-after by many today. Hill dealt with many controversial subjects through his writings including racism, slavery, oppression, failure, revolution, war and poverty. Persevering and then succeeding in spite of these obstacles using the Philosophy of Achievement, Hill stated, was the responsibility of every human.
Today's philosophy-of-success teachers still use the research formulas taught by Hill to expand their students' knowledge of personal development.
His 10 years penance with determination and devotion to interviewing constantly for 500 Personalities. This habit made him all time favorite guru and life changing speaker/author for millions of people around the world.
Napolean Hills written books are:
The Law of Success (1928)
The Magic Ladder To Success (1930)
Think and row Rich (1937)
How to Sell Your Way through Life (1939)
Success Through a Positive Mental Attitude (1960)
You Can Work Your Own Miracles (1971)
Napoleon Hill's Keys to Success: The 17 Principles of Personal Achievement
Grow Rich!: With Peace of Mind
The Master-Key to Riches
Succeed and Grow Rich Through Persuasion
Outwitting the Devil (2011)
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