Constructivism is a theory that believes moral judgments are not real things but they are constructed by practical reason in a rational procedure for resolving practical problems in front of us. Christine Korsgaard, a contemporary American philosopher, is a Kantian constructivist, whose theory I consider in this paper. She is a radical constructivist and disagrees with moral realism and denies moral truths even as abstract facts. According to Korsgaard moral judgments are constructed by rational agents. She believes moral and political principles are generally solutions to human practical problems. She justifies the normativity of moral obligations from this point that they are constructed by agent for resolving his problems. There are some objections to Korsgaard’s constructivism; one of them is to place humanity as the source of value. Keywords: Korsgaard, constructivism, practical problem, humanity. Introduction One of the traditional problems in moral philosophy is the nature and entity of moral truths and judgments. Do humans themselves make and construct them or are they facts and truths in the world which humans just discover? Are moral truths and values subjective or objective? Subjectivism and objectivism have been two old rivals in this question. But some philosophers have proposed a new theory between them that is called Constructivism. According to this theory, moral truths are not real and objective, but are constructed by human practical reason. In this view, an action is morally right when there is a sufficient reason to perform it. In this paper I will discuss Korsgaard’s constructivism. 1. Definition of Constructivism Constructivism is a theory about the justification of moral principles. It is the view that moral principles are the ones agents would agree with or endorse if they were to engage in a hypothetical or idealized process of rational deliberation. The differences about related criteria for this rational process and deliberation have produced several varieties of constructivism like Humean, Aristotelian, and Kantian.