Our analysis of Aristotle's main criticisms of Plato has already suggested thac his reaction against Platonism owes a good deal to his interest in natural science. The realisation of the need to begin the investigation of natural species with the concrete particulars must have deepened, even if it was not the sole cause of, his dissatisfaction with the theory of knowledge advocated by Plato in connection with the Forms. In attempting to document the growth of Aristotle's interests in natural science we have two precious pieces of evidence. First there is the connection which I have already noted between many of the place-names mentioned in the Historia Animalium and the areas of Greece where we know Aristotle lived during the so–called period of the travels from 347 to 335 b.c. The Historia Animalium contains some detailed information about the peculiarities of the animals, especially of the marine animals, found in and around the island of Lesbos, and particularly in the straits and lagoon of Pyrrha on that island, and Pyrrha figures again in the documentation of the two other main biological treatises, the de Partibus Animalium and the de Generatione Animalium. Aristotle's interest in biology no doubt dates from before the time he went to Asia Minor. His father was a medical man, and the problems of classification, particularly of the classification of natural species, were a much discussed topic in the Academy.

So far I have discussed three main features of Aristotle's intellectual development, the influence that Plato had on the young Aristotle, his reaction against the principal tenets of his master's philosophy, and the development of his interests in natural science, particularly in biology. But in concentrating on the main lines of his intellectual development during the earlier part of his life many other aspects of his work have necessarily been neglected. Yet from the beginning the range of problems that engaged his attention was wide, and it is now time to do more justice to this fact before turning to consider the chief characteristics of his work during the final period of his life.

As a young man in the Academy Aristotle would have discussed not only the ontological and epistemological questions connected with the theory of Forms, but also a large number of other subjects which certainly included logic or dialectic, ethics, politics and psychology. In each of these fields criticisms of Platonic theses are the startingpoint of some of Aristotle's own theories, and in some cases these criticisms may well have begun to take shape while he was still Plato's pupil. In logic, for example, the nature of dialectic and the difference between the dialectician and the sophist are discussed at some length by Plato in the later dialogues. Academic debates on these topics undoubtedly provide the background against which Aristotle developed his own complex classification of the different main branches of reasoning, demonstrative, dialectical, rhetorical and eristic, and it is natural to suppose, in this instance, that this analysis is, in the main, a product of the period of his first residence in Athens.

The Natural Image

It was said at the outset that Platonism and Christianism adopted different attitudes towards corporeal nature, the one regarding it as an obstacle to the soul's perfection, the other as an aid, and itself perfectible. The statement requires modification on both sides. Plato in his later works taught that the sensible world, being a copy of the intelligible, was a guide to the understanding of it, and his successors, under the influence of the Asiatic cults, adopted the same attitude to man-made images; while the early Christians, inheriting the Jewish abhorrence of idolatry, regarded as sacrilegious the representation of spiritual things through the medium of matter. Paganism and Christianism reacted to the same stimulus in contrary ways: the pagan cults which infected Platonism with theurgy stiffened the resistance of the Christians and turned their monotheism, for a time, into iconoclasm.

In the sensible world natural images are distinguished from artificial images by their causes. The causes of the former are the Forms: ‘ The Idea’, says Xenocrates, ‘is the exemplary cause of things which subsist naturally (κατα φυσιν).’ The causes of the latter are concepts in the mind of the artist: ‘Every artist possesses wholly the paradeigma in himself, and confers its shape upon matter.’ But if the Forms are themselves concepts in the Divine Mind, then both kinds of cause are concepts or thoughts, and the difference lies in the thinker, in the one case divine, in the other human.

St Augustine's life spanned almost eighty years of a period during which the ‘decline of the Roman Empire’ passed through its most dramatic, if not its most decisive, phase. Born into the Christian Empire of Constantine's successors, his youth saw the brief pagan reaction under Julian the Apostate, followed by the return to Christianity and the ever closer linking of the Empire to Christianity under the Emperors Gratian and Theodosius I. During the latter part of his life Roman paganism, which had rallied its forces during the last decade of the fourth century, was rapidly becoming a relic of the past, though it remained a force to be reckoned with. He witnessed not only an important phase in the Christianization of the ancient world; he also lived through some of its gravest military and political upheavals: the military disaster of Adrianople (378), the division of the Empire after Theodosius, the irruption of Vandals, Sueves and other barbarians into the western provinces of the Empire (406), the increasing barbarization of the Roman armies and of the imperial court, the sacking of the City of Rome by the Visigoths (410). These are some of the landmarks. The Vandal invaders of his own North Africa had just reached his episcopal city of Hippo as he lay on his deathbed. In an important sense his life may be said to coincide with the transition from antiquity to the Middle Ages. Augustine belonged to both worlds, in many ways, and not least intellectually. He received the kind of education which was typical of late antiquity, characterized by a predominantly literary or rhetorical outlook.

A Christian Platonist may be either a Platonist who requires to substantiate his speculations by a faith which transcends them, or a Christian who thinks of his faith, and desires to expound it, in terms intelligible to Platonists. St Augustine is the outstanding example of the former type, with whom could perhaps be associated from among the Greeks the ps.-Dionysius and Johannes Philoponus if we knew more about their origins. But the thinkers who built up the Greek Christian Platonist tradition and kept it within the bounds of orthodoxy mostly belonged to the latter: the Alexandrians, the Cappadocians, possibly the ps.-Dionysius, certainly St Maximus Confessor. And it was by following in the footsteps of these, but particularly of St Gregory of Nyssa, the ps.-Dionysius and Maximus, that Johannes Scottus Eriugena introduced this form of Christian philosophy to the West.

Three attitudes towards pagan learning were possible for the Christian: uncompromising acceptance, which led to heretical Gnosticism; uncompromising rejection, as shown by the early apologists and ascetics, favoured by the School of Antioch, and surviving into the Iconoclastic movement and into some forms of modern protestantism; and controlled acceptance, the attitude of the Alexandrians and of the writers discussed in this Part, which produced the Christian philosophy, or Christianism. This attitude acknowledges that the current philosophical systems contained elements of truth, a fact taken for granted by the Alexandrians and openly asserted, with particular reference to Platonism, by the Cappadocians, while rejecting what is evidently falsified by the Christian Revelation.

Pseudepigrapha

We know no Platonist later than the Old Academy and earlier than Eudorus who would have been interested in the Two-opposite-principles doctrine and the attendant horizontal stratification as attributed to Plato by Aristotle. Plutarch, who quotes Eudorus in a different context, knows the doctrine but makes very little of it. However, this does not mean that the doctrine was, before Eudorus, forgotten altogether. It rather seems that, while it lost its home in the Academy (or was relegated to some corner there), it was fully appropriated by the authors of post-Platonic Pythagorean writings. However, they often equate the two principles with Aristotle's form and matter, or with the active and passive principles of the Stoa. Syncretism makes its full appearance.

For our purpose it is best to distinguish three classes of these writings. The first consists of pseudepigrapha. Two names are of particular interest in this group: that of Ps.-Archytas and that of Ps.-Brontinus (assuming the passage by the latter as quoted first by Syrianus, and the passage by the former as quoted by Joh. Stobaeus to belong to the pre-Plotinian period).

Speaking of Brontinus, Syrianus assures us that the Pythagoreans were familiar with the doctrine that there is a principle higher than the two opposite principles. To prove it he quotes Philolaus as having said that God brought forth limit and the limitless; and he says that Archaenetus (there is hardly any reason to change this to Archytas) spoke of a cause prior to a cause and that Brontinus said of this cause that it is above intelligence and being (ousia), surpassing it in power and dignity.

The discussion on the character of Boethius: Platonic or Christian philosopher?

The impetus given to speculative thought by the existence of a court interested in intellectual activities petered out with the beginning of the tenth century. The invasions destroyed a good deal of the economic presuppositions on which centres of learning had to rely, and interrupted their lines of communication. There is good reason for the name of the ‘Dark Age’ given to the decades which followed the end of Carolingian civilization. While the importance and influence of the French monarchy was reduced by the rise of feudal principalities, and remained so during this period, after 950 the Ottoman dynasty were capable of re-establishing monarchical power in Germany and of reviving literary activities as the true heirs of Charlemagne. Under their rule Latin writing in prose and verse was cultivated in those Saxon lands where Christianity had been introduced only a few generations earlier. But their court never reached such importance as a forum where speculative questions were debated as had distinguished the circle of scholars round Charlemagne and his grandson. Single centres in West and Central Europe kept up a certain continuity of philosophical learning. In some monasteries and cathedrals the libraries, collected under the impulse of the Carolingian revival, were preserved, and so the tradition of study, linked to the keeping and copying of manuscripts, remained alive. Some of these books, handed on from antiquity, raised disturbing questions about the relationship of rational thought to Christian revelation in the mind of the monk or canon who read them.

Soul and the material world

Soul is, of Plotinus' three hypostases, the most wide-ranging and various in its activities. At the top of its range it lives on the highest level, in the world of Intellect, and with Intellect can rise in self-transcendence to union with the One. At the bottom, it is responsible for the formation of bodies in the visible world. But, however widely Soul may range, Plotinus never allows the distinction between it and Intellect to disappear (though it may in some passages become a little blurred), and he preserves its distinctive Platonic function of being the intermediary between the worlds of intellect and sense-perception, the immediate cause of the latter, and the representative in it of the former. Its proper and most characteristic activity is discursive thinking, reasoning from premises to conclusions; but it possesses the whole range of lower forms of consciousness, with the external activities appropriate to them; and it can and should, and, it seems, while it remains universal always does, rise above its reasoning to share Intellect's life of immediate intuitive thought. The initiative in this self-transcendence, as always in Plotinus, comes from above. It is Intellect which, by illuminating Soul, raises it to its own level. The relationship between the three hypostases in Plotinus is one of hierarchical distinction in unity. They are not cut off from each other. The One and Intellect are always present to Soul and acting on it, and this eternal presence and action is the most important thing which we (who are Soul) discover in philosophical reflection.

Porphyry's philosophical career

Most of the features of Neoplatonism that we have been sketching are evident in the work of Porphyry. So it will avoid repetition to give him more attention than might otherwise have seemed due to him. Porphyry was born in about 232, the year when Plotinus started to study philosophy at Alexandria. His parents were well-to-do Syrians, and he spent most of his boyhood, so far as we know, in the busy Phoenician city of Tyre. Even if he did not travel he had ample opportunity there to make the far from superficial acquaintance with the mystery cults and magical practices of the Middle East and beyond which his writings were to show. He probably knew several languages by the time he came to the West; he continued to read widely; and it was not a conventional compliment that Simplicius paid when he called him the most learned of philosophers. Three later stages of his career have left their mark on his philosophy, his attendance at Longinus' lectures, his friendship with Plotinus and a period away from Plotinus in Sicily.

Like other young foreigners of means but a little older than most, it would seem, Porphyry continued his education at Athens. Here the dominant influence was that of Longinus (who died in 272). The old-fashioned taste of the famous critic no doubt had some part in the clarity of Porphyry's style which was soon contrasted with Plotinus' indirectness. But this ‘living library and walking museum’, as Eunapius called him, lectured on philosophy too; and we have the testimony of both to their friendship.

The part of Porphyry's description of Plotinus at Rome which is most interesting to a historian of philosophy is of course his account of his master's method of teaching and writing, of his knowledge and use of previous philosophers and his relations with the philosophers of his own time. About all this Porphyry tells us a good deal which is helpful to our understanding of the Enneads. The lectures of Plotinus were not the formal, carefully arranged, set speeches developing a theme along lines fixed by established tradition which were customary in the philosophical schools of his time. The procedure in his school was informal, some said disorderly. Plotinus was a systematic and dogmatic philosopher, who had no doubt that he knew the right answers to the great philosophical questions which he treated: but he was not the sort of systematizer and dogmatist who cannot tolerate queries, objections and interruptions. He had a Socratic belief in the value of discussion, and once a discussion had started in his school it had to go on to the end, till the difficulties raised had been properly solved, however long it took. A story which Porphyry tells gives an excellent idea of the spirit in which Plotinus met queries and objections. A man called Thaumasius came into the school one day when Plotinus was arguing with Porphyry about the relationship between soul and body (the argument lasted three days) and demanded a set lecture suitable for writing down; he could not, he said, stand Porphyry's questions and answers. But Plotinus said ‘If we do not solve the difficulties which Porphyry raises in his questions we shall be able to say absolutely nothing suitable for writing down’.

The Peripatetic School from Theophrastus to Andronicus and Boethus

The development of the Peripatos down to the time of Strato exhibits two main aspects. First, philosophic-speculative interest is largely replaced by interest in all kinds of special and empirical knowledge, this knowledge no longer to serve as foundation for something higher, but terminal. Secondly, to the extent that philosophic interest is preserved at all, it often finds its satisfaction in non-theological, naturalistic, or even materialistic doctrines. For us only the latter aspect is important, as Plotinus' interest in empirical sciences is minimal.

Clearchus still seems to have refused to follow Aristotle's denial of the substantial character of the soul and presented him in a dialogue as having become convinced by what we should today call a telepathic experiment, that the soul can leave its body and return to it. He, then, would represent Aristotle's original Platonism.

As to Theophrastus, his so-called metaphysical fragment clearly proves that he retained Aristotle's speculative and theological interests. There is particularly no trace that he ever envisioned first philosophy to be anything but theology. The whole fragment is, from our point of view, remarkable mainly for three reasons. First, it shows to what extent Theophrastus connected the problems of Aristotle's Metaphysics with problems of the Two-opposite-principles system, including the derivation of everything from these principles and including the relation between these principles and evil. Secondly, it shows to what extent Theophrastus takes for granted that fundamentally all reality is divided into the spheres of the intelligible and the sensible, the former either including, or consisting of, mathematicals. Thirdly, it shows to what extent Theophrastus takes it for granted that knowledge of first principles will be of a particular type, non-discursive and described best as a kind of touching, so that one can be ignorant of these principles but not mistaken about them.

The impact of the Berengarian controversy

Anselm of Canterbury (1033–1109) in his literary work opened a new and highly individual chapter in the great controversy about the relationship of reason and belief. Before he became Primate of England in 1093 he had lived, studied and taught as a Benedictine in the Norman abbey of Bec, in contact with the spiritual and intellectual movements which at this time had their centre in the French-speaking countries of Western Europe. He had come from Aosta in the south-east corner of ancient Burgundy near the Lombard border. From his mother's side he was related to an important family of dynasts ruling in these parts. As a young man he was attracted by the revival of learning in France, like the Lombard Lanfranc before him, who in the fifties was prior of the newly founded monastery of Bec and had established there a school of some renown. Anselm joined him, first as a secular student and in 1060 as a monk. At this moment Lanfranc was deeply involved in the controversy with Berengar; he had attended the council of Rome, where the teaching of the famous master of Tours was condemned. When Anselm joined the monastic community this had been the great event of the previous year. Lanfranc himself was considered a pioneer in the revival of dialectical studies, and he was certainly anxious to strike the right balance between loyalty to the authority of biblical and ecclesiastical tradition and interest in a technically correct argument. Anselm remained in intimate contact with him for three years and became his successor as prior and head of the school, when Lanfranc left Bec on his appointment as abbot of St Stephens in Caen.

The sources of Augustine's reflection on human conduct, as of much of his thought, are the teaching of the Scriptures and the Church, and of Greek, particularly of Neoplatonic, philosophy. Sometimes, as we have noted, these two are in tension; in the present case, however, they blend completely in his mind. Indeed, it was here that he was above all impressed with the convergence he detected between Platonic and Christian teaching. His readiness to adopt other aspects of Platonic modes of thought, for instance in his discussion of soul and body, can in part be accounted for by this conviction of the similarity of their ethical bearings to those of Christian teaching. Tensions which can sometimes be detected between his Christian belief and his adopted philosophical concepts and language, tensions of the kind we have encountered, for instance, in his account of man as a soul using a body, are here totally absent.

Blessedness, as we have seen, was, for Augustine, the aim of philosophy. The wisdom which philosophy strove to attain would fill and satisfy all the deepest human needs and longings. Augustine was very ready to read back into Plato his own interpretation of what this love of wisdom consists in: Plato, he says, identified the supreme good, in the enjoyment of which man finds blessedness, with God. “And therefore he [Plato] thought that to be a philosopher is to be a lover of God.’ Affirmations of this kind pave the way for an almost wholesale adoption of Platonic notions, especially in the sphere of ethics.

Life and writings

What is known of Marius Victorinus' life is contained in the short notice given by St Jerome in his De viris illustribus and in the better known remarks made by St Augustine in the course of the narrative of his own conversion. African by birth and a rhetorician by profession, he taught in Rome under the Emperor Constantius. His fame as a rhetorician is attested not only by Augustine, but also by the statue which was erected to him in the Forum of Trajan in his lifetime, probably in the early fifties of the fourth century. An inscription of the late fourth century shows that it survived in Rome for at least two generations. He had written grammatical, rhetorical and logical treatises, commentaries on Cicero and Aristotle. He had also translated ‘books of the Platonists’, as Augustine called them, and some of Aristotle's logical treatises and, very probably, Porphyry's Isagoge ‘In extreme old age’, as Jerome tells us, he became a Christian. This must have been soon after the erection of his statue in Rome, in the early or mid fifties, at any rate before 357 or 358, when the flow of his Christian theological writings begins.

Victorinus was closely associated with the senatorial aristocracy which became the last stronghold of Roman paganism. Augustine's celebrated narrative of Victorinus' conversion to Christianity allows us to glimpse something of the force of the social and cultural links which had held the distinguished rhetorician allied to the traditions of his class. To break them required the strength of mind which Augustine's story stresses and which served Augustine as a model for his own conversion. Augustine had already read Victorinus' translations of Neoplatonic literature when his Milanese friend, Simplicianus, who had known Victorinus well, told him the story of his conversion.

The two chief—or even the sole—objects of interest to philosophy are God and the human soul. This was Augustine's view in his earliest works; and, ironically, the furthest departure from this view, that which owes most to philosophical inspiration, occurs in his long commentary on the book of Genesis, written some fifteen or twenty years later. It is here that he gives freest rein to the discussion of questions concerning nature other than human or divine. Nevertheless, physical nature never assumed the central place in Augustine's interests which the world of man and God held in them. The problems which interested Augustine most in this field were those which were forced upon his attention by the scriptural teaching. We shall confine our attention to three of them : the order of nature as related to God, natural function and development in the physical world, and time, all arising for Augustine from the doctrine of creation.

Two related thoughts form the kernel of Augustine's reflection on the physical world. These are that God created the world of nature and has ordered it, in the words of the Book of Wisdom often quoted by Augustine, ‘by measure and number and weight’ (xi. 20); and that this order in the world allows man to see the world as God's handiwork. The orderliness in which God created the world was universal and all-pervasive, except for such disturbances as were set up in it by sin or its effects. But this universal order, Augustine thought, was only apparent to men partially.