This paper extends the notion of the rational agent in economics by acknowledging the role of the unconscious in the agent's decision-making process. It argues that the unconscious can be modelled by a rational agent with his own objective function and set of information. The combination of both the conscious and unconscious agents is called the "dual agent". This dual agent presents rationally biased behaviors that may not disappear through aggregation, and could be potentially measured. It also provides a theoretical approach to the emotionally-driven actions. On the social sciences side, the paper pleads for a wider use of substantive rationality in the understanding of human behavior.