This analysis of the human need to persuade offers a new, creative, application of Aristotelian essentialism to human discourse. Using Thomas Aquinas's adaptation of essentialism as a starting point, Jeffrey J. Maciejewski argues that persuasion is natural to human beings and that it possesses dispositional properties that bring about stages of human action that ultimately harmonize the operations of the mind in addition to harmonizing human relationships. Aquinas's philosophy of human nature is reviewed and re-examined in order to discover why it is that humans need to persuade themselves and each other. The book should be of considerable interest to scholars of human nature, Thomist philosophy, and those interested in the history of rhetoric and rhetorical theory.