After Aristotle had completed his great speculative system, philosophy moves toward a new emphasis. Four groups of philosophers helped to shape this new direction, namely, the Epicureans, the Stoics, the Skeptics, and the Neoplatonist. They were, of course, greatly influenced by their predecessors, so we find that Epicurus relied upon Democritus for his atomic theory of nature, the Stoics made use of Heraclitus’ notion of a fiery substance permeating all things, the Skeptics built a method of inquiry upon the Socratic form of doubt, and Plotinus drew heavily upon Plato. What made their philosophy different, however, was not so much its subject matter as its mood and its emphasis. Its emphasis was practical, and its mood was self-centered. Philosophy became more practical by emphasizing the art of living. To be sure, each of these new movements of thought did involve speculative descriptions of the structure of the universe. But instead of working out blueprints for the ideal society and fitting individuals into large social and political organizations, as Plato and Aristotle had done, these new philosophers led people to think primarily of themselves and how they as individuals in a scheme of nature could achieve the most satisfactory personal life.
These new directions in ethics were brought about to a great extent by the historical conditions of the times. After the Peloponnesian War and with the fall of Athens, Greek civilization declined. With the breakdown of the small Greek city-state, individual citizens lost the sense of their own importance and their ability to control or perfect their social and political destiny. Individuals increasingly felt this loss of personal control over collective life as they were absorbed into the growing Roman Empire. When Greece became a mere province of Rome, men lost interest in pursing the speculative questions concerning the ideal society. What was needed was a practical philosophy to