There was still another Hellenistic school of philosophy, Skepticism, which was initiated by another of Zeno’s contemporaries, Pyrrhon of Elis (c. 360–c. 272 bc), and was destined to become of great importance for the preservation of detailed knowledge of Hellenistic philosophy in general. Pyrrhon had come to the conviction that no one can know anything for certain, nor can he ever be certain that the things he perceives with his senses are real and not illusory. Pyrrhon is said to have carried the practical consequences of his conviction so far that, when walking in the streets, he paid no attention to vehicles and other obstacles, so that his faithful disciples always had to accompany him to see that he came to no harm. Pyrrhon’s importance for the history of philosophy lies in the fact that one of the later adherents of his doctrine, Sextus Empiricus (flourished 3rd century ad), wrote a large work, Pros dogmatikous (“Against the Dogmatists”), in which he tried to refute all of the philosophers who held positive views, and in so doing he quoted extensively from their works, thus preserving much that would otherwise have been lost. It is a noteworthy fact that the British empiricists of the 18th century, such as David Hume (1711–76), as well as Immanuel Kant (1724–1804), derived most of their knowledge of ancient philosophy from Sextus Empiricus. Neo-Pythagoreanism and Neoplatonism
All of the philosophical schools and sects of Athens that originated in the 4th century bc continued into late antiquity, most of them until the emperor Justinian I (ad 483–565) ordered them closed in 529 because of their pagan character. Within this period of nearly 1,000 years, only two new schools emerged, neo-Pythagoreanism and Neoplatonism; both were inspired by early Greek philosophy, though only the latter would become historically important. Neoplatonism was established by Ammonius Saccas (fl. early 3rd century ad), who had been brought up as a Christian but had abandoned his religion for the study of Plato. Because Ammonius wrote nothing, his philosophy is known only through his famous disciple, Plotinus (205–270). But Plotinus did not publish anything either. His philosophy is known through the Enneads, a collection of his writings arranged by his disciple Porphyry (234–305), who also wrote a biography of Plotinus.
Although the philosophy of Plotinus (and Ammonius) was derived from Plato, it used many philosophical terms first coined by Aristotle and adopted some elements of Stoicism as well. Yet it was essentially a new philosophy, agreeing with the religious and mystical tendencies of its time. Plotinus assumed the existence of several levels of Being, the highest of which is that of the One or the Good, which are identical but indescribable and indefinable in human language. The next lower level is that of nous, or pure intellect or reason; the third is that of the soul or souls. There then follows the world perceived by the senses. Finally, at the lowest level there is matter, which is the cause of all evil. The highest bliss available to human beings is union with the One, or the Good, which is attained by contemplation and purification. That this is not a lasting state attained once and for all—like the status of the Stoic wise man, who was supposed never to lose his wisdom—is shown by the fact that Porphyry, in his biography, said that Plotinus had experienced this supreme bliss seven times in his life, whereas he, Porphyry, had experienced it only once.
The further history of Neoplatonism is extremely complicated. While Porphyry had emphasized the ethical element in Plotinus’s philosophy, his disciple in Syria, Iamblichus of Chalcis (c. 250–c. 330), mingled Neoplatonism with neo-Pythagoreanism, writing on the Pythagorean way of life and on number theory. Above all, he multiplied the levels of Being, or the emanations from the One, which enabled him to incorporate the traditional Greek gods into his system. Another branch of the school was founded in Pergamum, in western Asia Minor, by Iamblichus’s student Aedesius (died 355), who, with his own disciple Maximus of Ephesus (died 370), tried to revive the ancient Greek mystery religions, such as Orphism (see mystery religion). All of these developments became of great importance in the 4th century, when Emperor Julian the Apostate (c. 331–363) attempted to revive paganism. In the following century the Athenian school reached a new high point when Proclus (c. 410–485) combined the ideas of his predecessors into a comprehensive system. When Justinian closed all of the philosophical schools in Athens in 529, however, a branch continued to exist in Alexandria. The Athenian Neoplatonists found refuge at the court of the Persian king Khosrow I (died 579), and in 535 they were permitted to return to Athens. But gradually pagan philosophy as such died out, though it continued to influence the development of Christian philosophy and theology. Kurt von Fritz Medieval philosophy
Medieval philosophy designates the philosophical speculation that occurred in western Europe during the Middle Ages—i.e., from the fall of the Roman Empire in the 4th and 5th centuries ad to the Renaissance of the 15th century. Philosophy of the medieval period was closely connected to Christian thought, particularly theology, and the chief philosophers of the period were churchmen. Philosophers who strayed from this close relation were chided by their superiors. Greek philosophy ceased to be creative after Plotinus in the 3rd century ad. A century later, Christian thinkers such as St. Ambrose (339–397), St. Victorinus (died c. 304), and St. Augustine (354–430) began to assimilate Neoplatonism into Christian doctrine in order to give a rational interpretation of Christian faith. Thus, medieval philosophy was born of the confluence of Greek (and to a lesser extent of Roman) philosophy and Christianity. Plotinus’s philosophy was already deeply religious, having come under the influence of Middle Eastern religions. Medieval philosophy continued to be characterized by this religious orientation. Its methods were at first those of Plotinus and later those of Aristotle. But it developed within faith as a means of throwing light on the truths and mysteries of faith. Thus, religion and philosophy fruitfully cooperated in the Middle Ages. Philosophy, as the handmaiden of theology, made possible a rational understanding of faith. Faith, for its part, inspired Christian thinkers to develop new philosophical ideas, some of which became part of the philosophical heritage of the West.
Toward the end of the Middle Ages, this beneficial interplay of faith and reason started to break down. Philosophy began to be cultivated for its own sake, apart from—and even in contradiction to—Christian religion. This divorce of reason from faith, made definitive in the 17th century by Francis Bacon (1561–1626) in England and René Descartes (1596–1650) in France, marked the birth of modern philosophy. The early Middle Ages
The early medieval period, which extended to the 12th century, was marked by the barbarian invasions of the Western Roman Empire, the collapse of its civilization, and the gradual building of a new, Christian culture in western Europe. Philosophy in these dark and troubled times was cultivated by late Roman thinkers such as Augustine and Boethius (c. 470–524), then by monks such as St. Anselm of Canterbury (c. 1033–1109). The monasteries became the main centres of learning and education and retained their preeminence until the founding of the cathedral schools and universities in the 11th and 12th centuries. Augustine