We present a theory about human thought named the unconscious-thought theory (UTT). The theory is applicable to decision making, impression formation, attitude formation and change, problem solving, and creativity. It distinguishes between two modes of thought: unconscious and conscious. Unconscious thought and conscious thought have different characteristics, and these different characteristics make each mode preferable under different circumstances. For instance, contrary to popular belief, decisions about simple issues can be better tackled by conscious thought, whereas decisions about complex matters can be better approached with unconscious thought. The relations between the theory and decision strategies, and between the theory and intuition, are discussed. We end by discussing caveats and future directions.