Key to the Science of Theology is a foundational work in Latter-day Saint (LDS) theology, written by Parley P. Pratt and first published in 1855. It was intended as an introduction to Mormon doctrine for both curious outsiders and new members of the Church of Jesus Christ of Latter-day Saints.
The book lays out a bold, systematic view of theology as a “science”—something governed by eternal laws rather than abstract speculation. Pratt explains core LDS beliefs such as the material nature of God, the pre-mortal existence of spirits, ongoing revelation, and the idea that humanity can progress eternally toward godhood. He also emphasizes the physical reality of the spiritual world, arguing that spirit, matter, and intelligence are interconnected rather than divided into sacred and secular realms.
What makes the book especially distinctive is its confident, almost philosophical tone. Pratt blends biblical interpretation, reason, and early Mormon cosmology, presenting religion as something that can be understood logically as well as spiritually. Historically, the book played a major role in shaping early LDS thought and remains influential for its clear articulation of doctrines that set Mormonism apart from mainstream Christian theology.
