Moral reasoning refers to the psychological process of how an individual determines morality, good principles, and good action over bad principles and bad action. Formal study of moral reasoning is a relatively new development. It was not until the turn of the twentieth century that psychological models started to formally scrutinise and explain if and how a person comes to moral knowledge. Early explanations from Psychoanalysis and Behaviourism asserted that moral reasoning referred to a process that was external, received, and dictated by social convention and conditioning. This changed with the Cognitive-Developmental model, which asserted the opposite: that moral reasoning was internal, rational, and systematic. But the model invited critique, clarification, and challenge to its assumptions and claims – notably, from Ethics of Care, Social Domain Theory, and Social Intuitionism. Citing neuroscience research, Dual Process Theory gained traction in the evolving discourse with the assertion that people use discrete moral reasoning systems. As with the tapestry of complex moral situations that people face, current understanding of moral reasoning speaks to a multi-faceted process whereby a person sometimes seeks coherent principles; sometimes defers to fundamental interactions; sometimes reacts to powerful affect; and sometimes reflects biological characteristics in deciding whether something is good or bad.