The Xeelee Sequence deals with many concepts stemming from the fringe of theoretical physics and futurology, such as artificial wormholes, time travel, exotic-matter physics, naked singularities, closed timelike curves, multiple universes, hyperadvanced computing and artificial intelligence, faster-than-light travel, spacetime engineering, quantum wave function beings, and the upper echelons of the Kardashev scale. Thematically, the series deals heavily with certain existential and social philosophical issues, such as striving for survival and relevance in a harsh and unknowable universe and the effects of war and militarism on society.