Jean Meslier was a French Catholic priest (abbé) who was discovered, upon his death, to have written a book-length philosophical essay promoting atheism and materialism. Described by the author as his "testament" to his parishioners, the text criticizes and denounces all religions.

Materialism is a form of philosophical monism which holds that matter is the fundamental substance in nature, and that all things, including mental states and consciousness, are results of material interactions of material things. According to philosophical materialism, mind and consciousness are caused by physical processes, such as the neurochemistry of the human brain and nervous system, without which they cannot exist. Materialism directly contrasts with idealism, according to which consciousness is the fundamental substance of nature.