Revisions are proposed to the taxonomic model of human motivation of Forbes (2011) in order to incorporate a heretofore missing fourth life domain, the spiritual. The growing literature on spiritual motives is systematically reviewed in accordance with literature review standards for theory development (Templier & Paré, 2018) focusing on the objective of identifying comprehensive theoretical systems that explicitly incorporate the spiritual domain as one of a limited set of human life domains. The structure of the Forbes model is contrasted with thirteen theoretical systems that explicitly incorporate the spiritual as a fourth life domain. Consistent with the Forbes model, the spiritual domain is proposed to consist of three modes of existence (Being, Doing, Having) represented as justice motivation, moral motivation, and transcendental motivation, respectively, as well as both promotion and prevention goals within each of the three motives. Empirical evidence is reviewed in support of a revised heuristic device wherein the Spiritual domain is closely linked with the Intrapsychic and Interpersonal domains, but not the Instrumental domain, resulting in a pyramidal structure and corresponding set of five testable hypotheses.