St. Thomas Aquinas
St. Thomas Aquinas, in the Summa Theologica, understands the concept of the human person as “an individual substance of rational nature” (Th., I, q. 29, a. 4.), and the “substantial unity of soul and body” (Th., I, q. 76, a. 1.). These two concepts that St. Thomas presents to us are the basis for understanding and studying the human person and particularly the concept of dignity. For him, the person is the “individual substance of rational nature.” (S.