This is a challenger book. It systematically modifies the assumptions of the homo economicus and homo sociologicus by constructing a deeper foundation of human and corporate personhood. The new theory of homo psychologicus probes into a long-forgotten common sense: humans are rationally irrational homo psychologicus, as are companies. The homo psychologicus state of people and companies, or the desire of realizing who we are and who we are not, lays the foundation for our decisions on profits and stakeholder relationships.