The Master Key System is a personal development book by Charles F. Haanel that was originally published as a 24-week correspondence course in 1912, and then in book form in 1916. The ideas it describes and explains come mostly from New Thought philosophy.

Was the master key system banned?

The Master Key System was banned by the Church. It is said that when Haanel wrote The Master Key System, the Church found out about it and banned it. Hence, copies of the book became difficult to obtain and it is one of the reasons it's only now making a reappearance. ... It's enough that the Church banned the book.

What is the master key on the keyboard?

A master key is a key which will open all the locks in a set, even though each lock has its own different key.