The conception of God is both the most fundamental and the most difficult part of any scheme of religious thought. The Fathers were heirs to two traditions – the anthropomorphic accounts of God's loving activity in the Bible and the philosophical reflection on the changeless source of all being in Hellenistic thought. In the work of the Eastern Fathers in particular we see the interaction of these two traditions upon one another. The first four extracts chosen all come from the Eastern Church and illustrate that interaction.

Clement of Alexandria, writing towards the end of the second century, seeks to show how, on the one hand, poets and philosophers (above all Plato) and, on the other, Scripture point alike to the ineffability of God. In doing so he draws on the writings of Platonists of his own time. Origen held similar convictions, but the extensive nature of his expository and homiletic use of Scripture required him to work out their implications in more detail. The extract given here shows this concern leading him into an interesting discussion of the nature of religious language.

Basil's letter belongs to a more directly polemical context. The later Arians had claimed that it was logically impossible for the same God to be both essentially unknowable and yet known in Christian revelation. Basil meets the objection by drawing a distinction between God's essence and his attributes.

The passage from his brother Gregory of Nyssa shows the strongly religious character of this approach.

The affirmation of the divinity of Christ raises questions not only about the nature of the godhead of the kind dealt with in the last section, which led to the development of the doctrine of the Trinity. It raised questions also about the person of Christ himself – how could he be both God and man? The first extract comes from an attack by Tertullian on the teachings of Praxeas written about a.d. 210. Praxeas is probably a nickname meaning ‘busybody’. The distinctive feature of his teaching (not unlike what Origen appears to have objected to in Heraclides) was so strong an insistence on the unity of God that he was led to regard Father and Son as different names for God rather than indicative of different persons. This is the main problem dealt with by Tertullian in the work, but in the section given here he goes on to insist that Christ must be seen as both God and man without any diminution or loss of the essential characteristics of either nature.

The next five extracts come from the Eastern Church which was the scene of the main struggle to understand the full implications of the Church's confession on this issue. The first of them comes from a work of Eusebius of Caesarea, almost certainly written before the outbreak of the Arian controversy.

The extracts so far given have all been concerned with the substance of Christian doctrine. But the proper sources for determining Christian truth and the right use of them was also a matter for debate. The heading ‘Tradition and Scripture’ should not be allowed to suggest that these were thought of as rival sources in the way that has been characteristic of much later Christian history. In debate with the Gnostics of the second century insistence was placed both on the apostolic nature of the accepted writings of the New Testament and on the public nature of the Church tradition handed down from apostolic times. This is the main burden of the first passage of Irenaeus' work against the Gnostics.

Next we have Tertullian arguing for the importance of unwritten tradition in determining the Christian attitude on issues not dealt with in Scripture. But even more fundamental was the problem of how to interpret what was accepted as scriptural. The passage from Origen gives a clear account of the allegorical method of interpretation, which is so characteristic of his own work and of the Alexandrian tradition in general. In the next passage we see that approach applied by Dionysius, bishop of Alexandria shortly after Origen's time, in discussion with people who drew millenarian conclusions from the book of Revelation. The passage also displays an unusually acute literary critical sense in its discussion of the authorship of the writings that make up the Johannine corpus.

The most famous controversies of the patristic period were concerned with the Trinity and the person of Christ. But it will already be evident from the extracts dealing with these themes that the concern of the Fathers was to understand the persons of the Godhead in a way which safeguarded the reality of man's redemption. The extracts in this section deal with the fact of sin in human life and God's grace in relation to it.

In the first passage Origen uses his Platonism as a key to understanding the data of Scripture. He argues for a premundane fall of human souls as the only way in which God's justice can be squared with the apparent unfairness of differing human lots. This line of thought, however, did not commend itself to the Church as a whole.

The comparatively long extract from Gregory of Nyssa gives an account of the emergence of evil in the world in terms of man's free-will, without recourse to Origen's idea of the pre-existence of souls. The passage is one in which the Platonist character of Gregory's thought is particularly clear. The argument is developed in a way which not only frees God from responsibility for that evil but also sets the scene for his redemptive grace.

That redemption was effected by the death of Christ. But why was that death the means by which God worked man's salvation? The patristic age offers no clear-cut agreed answer to that question.

Christian understanding of God took the form, as we have seen, of a trinitarian belief in one God existing as three coequal ‘hypostases’ or ‘persons’. This is not clearly or self-evidently the teaching of Scripture. It is in relation to the Holy Spirit that scriptural teaching is least clear or self-evident. In the writings of the second and third centuries the Holy Spirit figures much less prominently than the Logos or the Son. The first passage, coming from that period, shows Origen reflecting on Scripture in the light of his general philosophical convictions about God in a way which was to seem to later generations to be wholly unacceptable.

The second passage comes from the Catechetical Lectures of Cyril of Jerusalem, delivered in the Church of the Holy Sepulchre during Lent to candidates for baptism at the coming Easter, about a.d. 350. They are concerned with man's need for the gifts of the Holy Spirit and show a strong reserve about speculations concerning his person. This may be due to the fact that they are lectures for catechumens, but is none the less characteristic of almost all Christian writing about the Spirit up to that time.

But the question of the true nature and status of the Spirit did become a prominent issue in the third quarter of the fourth century.

The Christian understanding of God involved not only the integration of anthropomorphism and mystery as illustrated in our first section. There was also the need to combine belief in the unity of God with the ascription of divinity to Christ, and also to the Holy Spirit.

The first passage is part of the transcript of a discussion between Origen and a bishop, Heraclides, whose orthodoxy had been called in question. Its discussion form helps to illustrate the nature of the problem as it was experienced not only by a sophisticated theologian but also by an ordinary bishop. We cannot be certain where or when the discussion took place; it is most likely that it was in Arabia towards the end of Origen's life (c. a.d. 244–9). The account is part of a papyrus found in Egypt in 1941.

The issue came to a head in the fourth century with the outbreak of the Arian controversy. Our second extract shows Athanasius dealing with one particular Arian argument – namely that the concept of God as the one unoriginated source of all being rules out the possibility of ascribing full divinity to the Word or Son.

But more was needed than simply to show that the full divinity of the Son was not an absurd concept. The Church needed to develop a positive way of understanding that divinity in relation to her continuing conviction of the unity of God.

The lines on which the Latin doctrines of the Church and sacraments developed were largely determined by controversy, much of it centered in North Africa. In the first two passages of this section we find two African bishops, Cyprian in the middle of the third century and Augustine early in the fifth, grappling with the questions of the identity and limits of the Catholic Church.

The election of Cornelius as bishop of Rome in a.d. 251 was disputed, and the impeccably orthodox but rigorist Novatian was consecrated as a rival bishop. For Cyprian the issue was clear-cut. The orthodoxy of Novatian's teaching was irrelevant. He had broken with the one and only Church and therefore had no part in her. In consequence, Novatianist baptism was worthless, and persons baptized as Novatianists who wished to join the Catholic Church must be rebaptized.

The Roman Church took the opposite view, holding that those who had received schismatical, as opposed to heretical, baptism did not need to be rebaptized if they became reconciled to the Catholic Church. When the Donatist schism broke out in North Africa in the third century, the Donatist party held to Cyprian's view of the matter, while the Catholic party adopted the Roman practice. Augustine's work On Baptism is directed against the Donatists. He could not hope to convince his opponents unless he could enlist the authority of Cyprian on his side.

The aim of this book is easier to describe than to achieve. Its purpose is to bring within the compass of a single volume a representative selection of extracts from the writings of the early Christian Fathers covering all the main areas of Christian thought. The importance of the Fathers as those who gave a distinctive and lasting shape to Christian theology is universally recognized. Those who have the time and the skill to read the writings of the Fathers in extenso and in the original will have no need of this volume. But we believe that there are an increasing number, not only of theological students, who would welcome a book which will introduce them to the thought of the Fathers at first hand. It is for such people that this book is designed.

The extracts are arranged topically. We have tried to select passages which make their point in a sufficiently self-contained manner to make sense when removed from their wider context, which are long enough not merely to declare a conclusion but to illustrate the kind of reasoning which leads up to it, and yet short enough to allow us to cover all the main areas of thought. The period is most renowned for its determination of ‘orthodox’ belief and denunciation of ‘heresy’. Some of the passages given come from directly polemical writings of this kind. But the Fathers did not indulge only in polemics.

Until the conversion of Constantine Christian attitudes to secular authority ran along lines inherited from Judaism. Secular authority was ordained by God for the government of the world; kings and rulers were to be respected and prayed for. At the same time no respect could be paid or prayer addressed to the gods of pagan society.

The first three passages of this section come from this early period and make these points. Irenaeus makes the general point that secular authority falls under the providence of the one God. The passages from Tertullian and Origen clearly reflect the hostility that Christians experienced in society. Tertullian writes against a background of actual persecution and Origen seeks to answer the charge of the pagan Celsus that Christians were guilty of an irresponsible abdication of their responsibilities to society.

Eusebius, in an oration delivered in Constantine's own presence in 335, writes in the new situation that followed the emperor's conversion. He draws on the language of Hellenistic writers on monarchy to produce a picture of the emperor that goes far beyond the traditional Christian respect for his office: Constantine is God's viceregent on earth. It is a picture of monarchy that leaves little room for any polarity of Church and state.

The last two passages come from Augustine, writing some eighty years later. The first is part of a public letter to a military commander, Boniface, justifying the suppression of Donatism.

From earliest times Christians reflected on the implications of their faith for their day-to-day lives. But Clement of Alexandria was the first Christian writer to give any extended attention to questions of ethics. His work The Rich Man's Salvation is interesting not only for its treatment of a perennial dilemma – that is, whether the imperatives of the gospel are to be taken in an absolute sense or not – but also for its evidence that by the beginning of the third century there were enough prosperous Christians to call for discussion of the particular injunction to sell all.

Hippolytus of Rome, a younger contemporary of Clement, gives us a picture of what was expected of the piety of the ordinary Christian of his time – though it can be questioned how far his words are prescription rather than description. Cyprian reveals the deeply Jewish character of the piety of the African church of this period: almsgiving is a good work which atones for sin.

The passages from Basil and Chrysostom, both from the latter half of the fourth century, come from a different world. Basil is prescribing the regime for a solitary, Chrysostom for the education of a young gentleman. Both writers are self-consciously Christian, yet both are much more deeply imbued than they realize with the educational and cultural heritage of the classical world.

One of the continuing debates of the patristic period was between those who took the biblical prophecies about the end of the present world and the coming of the next as literal predictions and those who took them more or less figuratively. The passage in which Dionysius of Alexandria discussed the interpretation of the Revelation of John (see pp. 145–51 above) provides an example of such controversy in the third century.

The passages in this section all come from the fourth and early fifth centuries. Rufinus provides a conventional and fairly literal exposition of belief in the resurrection of the flesh, and Chrysostom a harsh and uncompromising presentation of belief in the everlasting punishment of the wicked.

Gregory of Nyssa presents a very different picture. In a passage, the presuppositions for which are to be found in his deeply Platonizing view of evil and of the fall (see pp. 101–12 above), he expresses the belief that ultimately all mankind will be united with the divine and evil will be utterly annihilated. All punishment after death is remedial in intent, and the remedy will be effective. The fact that Gregory's views clearly owed much to Origen became a posthumous embarrassment to his memory when Origen's universalism, along with much else of his most characteristic teaching, came to be condemned as heretical.

Predictions of the imminent end of the world have been another recurrent source of dispute throughout Christian history.