Signal Fires is a novel concerned with the nature of time. Dani Shapiro explores philosophies of metaphysics in order to propose the idea that time is nonlinear, and that people are interconnected through time and space. The term metaphysics is derived from the Greek “meta ta physika,” which means “after the things of nature.” Metaphysics is therefore a study of what can’t be studied through the analysis of material objects. It proposes that there is an essence to everything, but this essence is not necessarily definable or witnessable. The three major categories of metaphysics are general metaphysics, physical metaphysics, and religious metaphysics.

Physical metaphysics is concerned with the structures and origins of the universe. Waldo is interested in physical metaphysics as demonstrated by his knowledge of the stars and universe. When Waldo compares a dying star’s matter being reincarnated into other celestial objects to a human dying but living on in spirit, he is engaging in physical metaphysics. He doesn’t know how or why these things happen; he just knows that they do happen.

Religious metaphysics is concerned with how and why religious ideology came to be, and how it continues to structure society. Metaphysics is therefore one of the few academic disciplines that treats science and religion as equally important; a scientist can’t necessarily explain the formation of the universe just as a practitioner of Christianity can’t necessarily explain how and why Jesus walked on water.