As a Man Thinketh is a literary essay of James Allen, published in 1902. The title is influenced by a verse in the Bible from the Book of Proverbs chapter 23 verse 7, “As a man thinketh in his heart, so is he.”
The full passage, taken from the King James Version, is as follows:
"Eat thou not the bread of him that hath an evil eye, neither desire thou his dainty meats: For as he thinketh in his heart, so is he: Eat and drink, saith he to thee; but his heart is not with thee. The morsel which thou hast eaten shalt thou vomit up, and lose thy sweet words."
The passage seems to suggest that one should consider the true motivations of a person who is being uncharacteristically generous before accepting his generosity - while in the title and content of James Allen's work the passage is in a different context; In the Bible the passage is referring to another person, and in James Allen's work the passage is adopted to primarily refer to the reader himself.
This version of the classic book includes a biography about the life and times of James Allen.