. For Aristotle, psychology was a study of the soul. Insisting that form (the essence, or unchanging characteristic element in an object) and matter (the common undifferentiated substratum of things) always exist together, Aristotle defined a soul as a "kind of functioning of a body organized so that it can support vital functions." In considering the soul as essentially associated with the body, he challenged the Pythagorean doctrine that the soul is a spiritual entity imprisoned in the body. Aristotle's doctrine is a synthesis of the earlier notion that the soul does not exist apart from the body and of the Platonic notion of a soul as a separate, nonphysical entity. Whether any part of the human soul is immortal, and, if so, whether its immortality is personal, are not entirely clear in his treatise On the Soul. The influence of Aristotle's philosophy has been pervasive; it has even helped to shape modern language and common sense. His doctrine of the Prime Mover as final cause played an important role in theology. Until the 20th century, logic meant Aristotle's logic. Until the Renaissance, and even later, astronomers and poets alike admired his concept of the universe. Zoology rested on Aristotle's work until British scientist Charles Darwin modified the doctrine of the changelessness of species in the 19th century. In the 20th century a new appreciation has developed of Aristotle's method and its relevance to education, literary criticism, the analysis of human action, and political analysis.Epicurus, 341 BC- 270 BC, expired. Epicureanism is a system of philosophy based chiefly on the teachings of Epicurus. The essential doctrine of Epicureanism is that pleasure is the supreme good and main goal of life. Intellectual pleasures are preferred to sensual ones, which tend to disturb peace of mind. True happiness, Epicurus taught, is the serenity resulting from the conquest of fear of the gods, of death, and of the afterlife. The ulti...
