In this edition of the book, Sire defines a worldview as a “commitment, a fundamental orientation of the heart.” This definition contrasts with the view, implied in the previous editions, of a worldview as a “set of presuppositions” (xii).

Theism denotes a belief in God as the creator of the universe; specifically, theists believe that God can reveal himself to humankind by means of divine intervention in the world (e.g., in Christianity, by God becoming man in the form of Jesus Christ). This belief in God’s revelation distinguishes theism from deism on the one hand and atheism on the other. Sire’s book is essentially an argument on behalf of Christian theism by contrasting it with rival worldviews that have grown up in the modern West.

Naturalism denotes the belief that all of reality is explainable by laws of science; naturalism rejects the existence of God or the idea that there is purpose in the universe. Sire sees naturalism as the natural result of rejecting belief in a personal God and the next stage after deism in the development (in his view, decline) of Western thought.