Socrates argues that individuals can continue to behave morally when trying to explore virtue, distinguishing between copying a moral person’s actions and acting on the basis of virtue itself. This study proves the limitations of South Korea’s moral education, which values moral knowledge as a driver of moral behavior, by analyzing the art of measurement presented by Socrates as a method of recognizing virtue. Consequently, Protagoras was examined to identify the characteristics of the art of measurement, and “all pleasure is good” and “knowledge directly drives action” was problematized. The study concluded that moral knowledge is not a decisive factor in guiding moral behavior in the right direction.