The Fundamentals or The Fundamentals: A Testimony To The Truth edited by A. C. Dixon and later by Reuben Archer Torrey is a set of 90 essays in 12 volumes published from 1910 to 1915 by the Bible Institute of Los Angeles. They were designed to affirm orthodox Protestant beliefs, especially those of the Reformed tradition, and defend against ideas deemed inimical to them. They are widely considered to be the foundation of modern Christian fundamentalism.
The essays were originally financed by Lyman Stewart in 1909 to set out what they believed to be the fundamentals of Christian faith. These were to be sent free to ministers, missionaries, Sunday School superintendents and others active in Christian ministry.
The volumes defended orthodox Protestant beliefs and attacked higher criticism, liberal theology, Catholicism (also called by them Romanism), socialism, modern philosophy, atheism, Christian Science, Mormonism, Millennial Dawn (an early term for a particular Christian Bible Student movement which mostly later became the "Jehovah's Witnesses" denomination), Spiritualism, and evolutionism (an article by geologist George Frederick Wright). (Wright did not attack biological evolution.)
Read more about The Fundamentals: Contents of The Fundamentals (and Authors)