(Root Homepage - Original Language Version Homepage)

Original language texts and translations on the Early Church Texts website, arranged by theme
(A complete list arranged alphapetically by author can be found here.)
 

Scroll down or click on links:

Apocryphal Writings, Apostolic Fathers, Arius and Arian Controversy, Asceticism/Monasticism, Atonement and Salvation, Baptism, Canons, The "Catholic Church", Christianity and Philosophy, Christmas, Christology, Church and State, Councils, Creeds, Docetism, Donatism, Easter, Ebionites, Ethics and Lifestyle, The Eucharist, Free Will and Grace, Gnosticism, God (Understanding the Nature of), The Holy Spirit, Judaism, Martyrdom, The Military and War, Ministry and Episcopacy, Monarchianism, Monasticism, Montanism, Nativity of Christ, Origenist Controversy, Paganism and Christianity, Papacy, Pelagius and Pelagianism, Persecution, Scripture, Slavery, Tradition, Trinity

You can also access a complete list of texts arranged alphabetically by author, or the complete list of the printable texts on the site (the same contents as the alphabetical complete list, but with a little more information and organised by Creeds and Councils, Greek Writers and Latin Writers sections.) The subscription site also gives carefully indexed links to complete Greek and Latin texts on external sites such as Google Books. Here is a complete list of authors for whom links to complete texts are available. There are also indexed links to the texts of Church Councils in Mansi's "Councils" volumes (Sacrorum Conciliorum Nova et Amplissima Collectio).

THE SUBSCRIPTION VERSION OF THE SITE HAS ALL OF THE TEXTS LISTED BELOW, WITH TRANSLATIONS ALONGSIDE, PRINTABLE VERSIONS*  OF THE TEXTS, ALL INDEXED BY AUTHOR AND THEME, PLUS MUCH MORE (including extensive direct links to complete Greek and Latin texts on external sites).
*
The specially prepared printable versions of the on-site texts are available only on the full (not trial) subscription version of the site.
Click here for more information about the subscription version of the site.
Click
here to go to the online sign up page for individuals.

Navigate to the site's original language texts by using the "Authors" menus from the site homepage or any of the main text pages of the site. (The subscription version of the website lets you navigate texts through a "Texts" or "Themes" menu.)

 

Apocryphal Writings
James, Protoevangelium of, 11-25

 

Apostolic Fathers (with links to scanned version of complete text for all listed below and 2 Clement and  Polycarp to Philippians)
I Clement 40 - 42, 44
Didache: Complete text
Diognetus: Epistle to 5-7
Ignatius: Trallians 9-10; Magnesians 8-10; Romans 5; Smyrnaeans 8
Polycarp: Martyrdom of 1-7
Shepherd of Hermas: Complete text

 

Arius and Arian Controversy
Arius' Confession of faith to Constantine from Eusebius, Historia Ecclesiastica, 1.26
Arius' Letter to Alexander of Alexandria from Athanasius, De Synodis, 16
Arius' Letter to Eusebius of Nicomedia from Theodoret,
Historia Ecclesiastica, 1.4. (or 5),1-4
The Thalia of Arius from Athanasius
Adversus Arianos Oratio Prima , 1,5  and then De Synodis, 15
Alexander of Alexandria on Arius from Eusebius,
Historia Ecclesiastica, 1. 6. 4 ff.
Letter of the Council of Nicaea to the Egyptian Church from Socrates, Historia Ecclesiastica, 1. 9
Socrates on Arius and the beginnings of the Arian Controversy from
Socrates, Historia Ecclesiastica, 1.5
Sozomen on Arius from Historia Ecclesiastica, 1.15
Second Creed of Sirmium - 357 (The Blasphemy) from Hilary,
De Synodis,
 11
Fourth Creed of Sirmium - 359 (The Dated) from Athanasius
, De Synodis, 8
Homoian Creed of Constantinople - 360, from
Athanasius, De Synodis, 30
Canons of the Council of Constantinople - 381
Creeds of Nicaea (325) and Constantinople (381 - Nicene)

 

Asceticism/Monasticism
Antony, the Life of, from Athanasius, Vita S. Antonii,  5 - 10 and 89 - 94
Basil,
Letters, 2 - to Gregory of Nazianzus (c. 358)
Basil,
The Longer Rule, Regulae Fusius Tractatae, VII (extracts)
Coenobites, Anchorites and Remoboth, from Jerome,
Epistle XXII, 34-35
Evagrius, Eight Logismoi,
De Octo Vitiosis Cogitationibus
Gangra Council Canons
Jerome's temptations in the desert from
Letter XXII to Eustochium, section 7
Jerome's Letter XLV to Asella in which he describes the ascetic life of some Roman Christian women and his departure from Rome (385)

Jerome's
Letter CXXVII to Principia, about Marcella, following her death in 410

Macrina St (about), from Gregory of Nyssa,
Life of St Macrina
, excerpts
Martin of Tours (about), from Sulpicius Severus,
Vita Martini,  10
Origen
On Prayer, from De Oratione, XXXI - XXXIV
Pachomius (about), from Sozomen,
Historia Ecclesiastica, 3. 14
Pseudo-Macarius, Homily 18 on Christian Perfection

 

Atonement and Salvation
Athanasius - On The Atonement - From De Incarnatione Verbi, 7-9
Augustine - On The Cross - Contra Faustum, 14. Augustine responds to the Manichaean Faustus' views about the verse: 'Cursed is every one that hangeth on a tree'.
Irenaeus - Recapitulation in Christ - Adversus Haereses, 3.18.1 and 5.21.1; the salvation lost in Adam is regained in Christ.
Rufinus - The Cross of Christ - From Commentarius In Symbolum Apostolorum, 14 - 17; Including the passage about the incarnate Christ as 'bait' for the devil.

 

Baptism
Cyprian's letter to Pompey - about Stephen's views on there being no need to rebaptise 'heretics'
Cyprian's letter to Quintus - about the rebaptism of 'heretics'
Cyril of Jerusalem - This passage from the Catechetical Lectures, 19 outlines the significance of baptism.
In The Didache - chapters 7 - 10
Gregory of Nyssa On Baptism - In Baptismum Christi, excerpt
In Justin Martyr - Apology, 1. 61
In Tertullian - De Corona, 3

 

Canons
The Canons of Carthage against Pelagianism
The Canons of Chalcedon
Canons of Constantinople
Canons of Elvira
Canons of Ephesus
Canons of Gangra
Canons of Nicaea 325

 

The "Catholic Church"
Cyprian - On the Unity of the Church - On the Unity of the Church, 4-6
Cyril of Jerusalem - Catechetical Lecture 19
Ignatius - Letter to the Smyrnaeans, 8
Irenaeus - The Rule of Faith - The faith of the Church the same throughout the world; from Adversus Haereses, 1. 2 - 3
Siricius - Decretal to Himerius about papal authority
Vincent of Lerins - Commonitorium, 2. 4 - 3. 8 and 23. 54 - 58

 

Christianity and Philosophy
Augustine and Cicero - Confessions, 3. 6-9
Augustine on Christianity and Pagan learning - De Doctrina Christiana (On Christian Doctrine), 40 (60, 61)
Augustine on Plato's Forms / Ideas, De Diversis Quaestionibus Octoginta Tribus, 46
Basil on Greek Literature - Address to Young Men on the Right Use of Greek Literature
Clement of Alexandria - Stromateis, 1.5 .28
Gregory Thaumaturgus - In Origenem Oratio Panegyrica, extracts from 6 and 13 (Origen and Philosophy)
Jerome - Ciceronian or Christian? - Jerome, Letter 22 to Eustochium, section 30
Justin Martyr (Christians before Christ) - Apology 1.46
Justin Martyr - Christ and Socrates - Apology 2.10
Synesius, Letter 105 to his brother (about Synesius' appointment as bishop)
Tertullian  (What has Athens to do with Jerusalem?) - De Praescriptione Haereticorum, 7


Christmas - See under Nativity of Christ

 

Christology
Apollinaris of Laodicea - a number of fragments from Lietzmann
Apolliniaranism, critique of -
Epistle 101 (part of)
Athanasius - Oratio Contra Arianos III, 29-34
Athanasius - Tomus ad Antiochenos, 3 - 7
The Chalcedonian Definition - from the Council of Chalcedon - Agreed at the Fourth Ecumenical Council at Chalcedon in 451
Constantinople, Council of, 448 - The condemnation of Eutyches
Cyril of Alexandria 12 Anathemas
Cyril's letter to John of Antioch
Cyril's 2nd letter to Nestorius
Eutyches - Condemnation of at Constantinople 448 - The testimony of Eutyches at the 448 Council, summoned by Flavian, Patriarch of Constantinople, and his condemnation for his monophysite views. (Extracts from Mansi, Conciliorum)
Gregory of Nazianzus Nativity Oration - Oratio, 38 (1 - 4, 13 - 18)
Hilary on Two Natures of Christ - De Trinitate Libri Duodecim, 9. 14 and 10. 19
Leo 8th Sermon on the Nativity - SERMO XXVIII [Al. XXVII]. In Nativitate Domini VIII.
Leo's Tome (Complete text) - Epistola XXVIII. Ad Flavianum Episcopum Constantinopolitanum Contra Eutychis Perfidiam Et Haeresim
Nestorius - 2nd Letter to Cyril
Tertullian on Christ's Two Natures - Adversus Praxeam,  27
Tertullian on The Incarnation -
Apologeticus pro Christianis (Apology),  21: 10-14
Theodoret, Eranistes - extracts from relative to the Person of Christ
Theodore of Mopsuestia -
De Incarnatione, 7

 

Church and State
Ambrose's letter to Marcellina (Letter 20)
Ambrose's Letter to Theodosius (Letter 51)
Codex Theodosianus - Various Edicts
Ambrose, Letters 17 and 18 to Valentinian
The Edict of Galerius (311 edict of toleration as given in Lactantius Liber De Mortibus Persecutorum)
The Edict of Milan (313 - as given in Lactantius Liber De Mortibus Persecutorum)
Eusebius - Constantine's vision of the cross (Vita Constantini, 1. 26-31)
Eusebius - The Neronian Persecution (Historia Ecclesiastica, 2. 25)
Hadrian's Rescript to Caius (Eusebius, Historia Ecclesiastica, 4.9 and Latin from Rufinus' translation)
Julian's Rescript on Christian Teachers (Letter 36)
Lactantius - The beginning of persecution under Diocletian (Liber de Mortibus Persecutorum, XI - XIII)
Lactantius - Constantine's vision of the cross (Liber de Mortibus Persecutorum, XLIV)
Libellus of the Decian Persecution (From June 250)
Marcian and Valentinian edict following Council of Chalcedon, requiring conformity
The Martyrdom of Alban (Bede, Historia Ecclesiastica Gentis Anglorum, 1. 7)
The Martyrdom of Polycarp (The Encyclical Epistle of the Church at Smyrna (1-22))
The Passion of Perpetua (Complete Greek and Latin Text)
Pliny's Letter to Trajan about how to deal with Christians (Letter 10.96 in Loeb 1915 edition)
Tacitus - Persecution under Nero (Annales ab excessu divi Augusti, 15.44)
Socrates on The Statue of Eudoxia (Historia Ecclesiastica, 6. 18. 1-5)
Symmachus's Plea to Valentinian II (included after Ambrose's Letter 17 in Migne)
Tertullian - The Blood of Christians is Seed (Apologeticus pro Christianis (Apology), 48 - 50)
Tertullian on Christians and the Emperor (Apologeticus pro Christianis (Apology), 29 - 33)
Trajan's Reply to Pliny (Letter 10.97 in Loeb 1915 edition)

 

Councils
Antioch - creeds of 341 council
Carthage - canons of 418 council against Pelagianism
Chalcedon (451)
        Canons
        Definition (creed) of 451 council
        Edict of Marcian and Valentinian following the council and requiring conformity 
        The Tome of Leo
        Letter of the Council to Leo
Constantinople - canons and creed of 381 council
Elvira - canons of c. 305 council
Ephesus - canons of 431 council - plus also Cyril's twelve anathemas
                - John of Antioch - Resolution of The Conciliabulum at Ephesus (431)
Gangra - canons of council (c. 340 - 360)
Nicaea - canons, creed and letter to Egyptian church of 325 council
Sardica (Serdica) - creed of 343 western council and Socrates' account (Historia Ecclesiastica, 2. 20)
Sirmium - first creed of (351), second creed of (357), third creed of (359)
Tyre (335) - Sozomen on Athanasius and the council of (Historia Ecclesiastica, 2. 25)

 

Creeds
Creeds of Antioch (341)
Creed of Caesarea (as in Eusebius' letter to his church on the creed of Nicaea, in Socrates - Historia Ecclesiastica, 1. 8)
Creed of Chalcedon (451)
Creed of Constantinople (381)
Homoean Creed of Constantinople (360)
'Long Lines' or 'Macrostichos' (345)
Creed of Nicaea (325)
The 1st Creed of Sirmium (351)
The 2nd Creed of Sirmium (357)
The 4th Creed of Sirmium (359 - The 'Dated')
Creed of Western Council of Sardica (343)
Irenaeus - The Rule of Faith
Origen - The Rule of Faith
Tertullian - The Rule of Faith
The Old Roman Creed

 

Docetism
Ignatius on docetism - Trallians, 9-10

 

Donatism
Optatus, on the origins of - De Schismate Donatistorum, 1. 15-19

 

Easter
Etheria - Easter in Jerusalem (Silviae Vel Potius Aetheriae Peregrinatio Ad Loca Sancta (chapters XXIX - XL))
Gregory of Nazianzus - Oration 1 on Easter (Oratio 1 - In sanctum Pascha et in tarditatem)
John Chrysostom - Easter Sermon (as in
Migne PG, Vol. 59, Col. 721)
Letter of Nicaea to the Egyptian Church - (including about the date of Easter, as in Socrates, Historia Ecclesiastica, 1. 9 )
Quartodeciman Controversy - Eusebius, Historia Ecclesiastica, 5. 23-25

Ebionites
Irenaeus on the Ebionites - Adversus Haereses, 1.22

 

Ethics and Lifestyle
Augustine and 'Just War' - Contra Faustum Manichaeum, 22. 69-76
Basil against Usury - Homilia in Psalmum XIV - (extracts, including most of 1, first part of 2, part of 4 and whole of 5)
Canons of the Council of Elvira (c. 305)
Christians and the military - Augustine, Letter 189
Chrysostom (John) on Rich and Poor - Homily XXXIV on I Corinthians 13: 8
Clement of Alexandria: The Salvation of the Rich - Liber Quis Dives Salvetur, 11-17
Epistle to Diognetus: chapters 5-7
Gregory of Nazianzus on The Hospital of Basil - Oration 43,63
Gregory of Nyssa - On Slavery - Expositio in Ecclesiasten - beginning of Homily IV
Gregory of Nyssa - Against Usury - Oratio Contra Usurarios (excerpts)
No Pagans in the Army - (from Codex Theodosianus)
Tertullian on Military Service
- De Corona, chapters 1, 11 and 12
Tertullian to his wife - Ad Uxorem, the whole of the first book

 

The Eucharist
Augustine Sermon on - Sermon 272
Chrysostom - Awe at the Eucharist - Homily 9 on Repentance
Cyprian - Wine mixed with water to be used - Epistle 63 to Caecilius (extracts)
In The Didache - Didache, chapters 7-10
In Irenaeus - Adversus Haereses, 4. 31 (Harvey edition)
In Justin - Apology, 1. 65-67
In Tertullian - De Corona, 3

 

Free Will and Grace
Augustine on Free Will - City of God, 22.30.3
Irenaeus on the Image and Likeness of God - Adversus Haereses, extracts from books 3, 4 and 5
John Chrysostom on Free Will - from Homily 16 on Romans 9
Pelagius on Free Will - From Augustine, De Gratia Christi, 5
Pelagius - Letter and Confession of Faith to Innocent I (417)

 

Gnosticism
Irenaeus on Basilides - Adversus Haereses, 1.19

 

God, understanding nature of
Basil on God's Essence and Attributes - Letter 234
Clement of Alexandria on God's Ineffability - Stromateis, 5.12
The self-emptying of the Godhead - Gregory of Nyssa, Against Eunomius, 5. 5

 

The Holy Spirit
Augustine on The Trinity and The Holy Spirit from De Trinitate, 5.10.11 - 5.13.14; 15.17.30 - 15.17.31; 15.19.37
Augustine on The Trinity and The Holy Spirit and whether The Spirit proceeds from The Father only or from The Father and The Son, from In Evangelium Ioannis tractatus, 99: 6 - 9
Basil on the Holy Spirit - Letter 159 - to Eupaterius and his daughter (c. 373)
The Deity of the Holy Spirit - Gregory of Nazianzus, Oration 31, 9-11, Theological Oration, 5
Heresy about the Holy Spirit - Athanasius, Ep. Ad Serapionem, 1.1

 

Judaism
Ambrose and the synagogue in Callinicum - Ambrose, Letter 40
Christianity and Judaism - Ignatius, Magnesians 8-10
Ebionites - Irenaeus on - Adversus Haereses, 1.22

 

Martyrdom
Ignatius - Romans, 5
Perpetua and Felicitas - The Passion of Perpetua (Complete Greek and Latin Text)
Polycarp, The Martyrdom of - (The Encyclical Epistle of the Church at Smyrna (1-22))

 

The Military and War
Augustine and 'Just War' - Contra Faustum Manichaeum, 22. 69-76
Christians and the military - Augustine, Letter 189
No Pagans in the Army - from Codex Theodosianus
Rain in answer to Christian prayer - Eusebius, Historia Ecclesiastica, 5. 5
Tertullian on Military Service - De Corona, 1, 11 and 12

 

Ministry and Episcopacy
Augustine - On the Episcopate - City of God, 19. 19
Clement of Rome - I Clement, 40 - 42, 44
Cyprian - On the Unity of the Church - On the Unity of the Church, 4-6
Ignatius - Ministry and Sacraments - Smyrnaeans, 8
Irenaeus - On Tradition - Adversus Haereses, 3.2.1 - 3.4.2
Jerome - Letter 146 to Evangelus -  about Deacons, Presbyters and Bishops

 

Monarchianism
Dionysius of Rome - Against the Sabellians
Epiphanius on Sabellius - Adversus Haereses (Panarion), 62
Eusebius on the Two Theodoti - Historia Ecclesiastica, 5.28



Monasticism
See under Asceticism

 

Montanism
Eusebius - Origins of Montanism - Historia Ecclesiastica, 5.16
Hippolytus - Montanist Prophets - Refutation of All Heresies, 8.19

 

Nativity of Christ
Etheria - Epiphany in Jerusalem - (Silviae Vel Potius Aetheriae Peregrinatio Ad Loca Sancta (chapter XXV))
Gregory of Nazianzus - Nativity Oration - Oratio, 38 (1-4, 13-18)
John Chrysostom - Homily on the birthday of Christ (a - There is something which long ago patriarchs painfully longed for - about date of Christmas)
John Chrysostom - Homily on the birthday of Christ (b - I see a strange and novel mystery)
John Chrysostom - Homily VI on Matthew 2: 1-2, about the Magi, the star and Herod. The full homily.
John Chrysostom - Homily VII on Matthew 2, about the Magi, the star and Herod (continued). The full homily.
John Chrysostom - Homily VIII on Matthew 2, about the Birth of Christ, The Magi, the flight into Egypt and the spiritual life of Christian women and men in the Egyptian desert. The full homily.
John Chrysostom - Homily IX on Matthew 2, about the slaughter of the innocents, the flight into Egypt, the return to Nazareth and the folly of thinking too highly of noble lineage or wealth.  The full homily.
Leo - Sermon XXVII (8th on the Nativity)
Protoevangelium of James (11-25)

 

Origenist Controversy
Jerome - Letter 33 to Paula (fragment of)
Jerome - Contra Joannem Hierosolymitanum, 7
Jerome - Letter 127 to Principia (after the death of Marcella)
Rufinus - Preface to Origen's De Principiis
Socrates defends Origen - Historia Ecclesiastica 6. 13

 

Paganism and Christianity
Augustine - Philosophy and Theology / Christianity and Pagan learning from De Doctrina Christiana (On Christian Doctrine), 40 (60, 61)
Basil on Greek Literature - Address to Young Men on the Right Use of Greek Literature
Jerome - Ciceronian or Christian? - Jerome, Letter 22 to Eustochium, section 30

Lucian - The Passing of Peregrinus, 11-14
Minucius Felius - Octavius - excerpts from chapters 5 - 12 (speech of Caecilius)
Origen - Celsus' Objections Against Christianity - various extracts from Contra Celsum
(See also under "Christianity and Philosophy".)

 

Pelagius and Pelagianism
Augustine - Nature and Grace - De Natura et Gratia, 3 - 6; a helpful summary of Augustine's doctrine of 'grace'.
Augustine - Pelagianism - De Haeresibus , 88
Augustine - Pelagius' denial of Original Sin - From Augustine, De Peccato Originali , 13
Canons of Carthage against Pelagianism (418) - Canons against Pelagianism agreed at the Council of Carthage in 417 or 418
Julian of Eclanum - Baptism - Liber I ad Turbantium, as found in Augustine, Contra Secundam Juliani Responsionem Imperfectum Opus, 1.53
Pelagius - On Free Will - Quoted in Augustine, De Gratia Christi, 5
Pelagius - Letter to Demetrias - Epistola ad Demetriadem, 16
Pelagius - Letter and Confession of Faith to Innocent I - Sent in 417. The letter is reconstructed from fragments found in Augustine.


Papacy
The Letter of the Council of Chalcedon to Leo
Flavian - Appeal to Leo following the Robber Council
Siricius - Decretal to Himerius about papal authority
 


Persecution
Dio Cassius - Persecution under Domitian - Historia Romana, 67.14
Eusebius - The Neronian Persecution - Historia Ecclesiastica, 2.25
Hadrian's Rescript to Caius (Eusebius, Historia Ecclesiastica, 4.9 and Latin from Rufinus' translation)
Lactantius - The beginning of persecution under Diocletian - Liber de Mortibus Persecutorum, XI-XIII
Libellus of the Decian Persecution - (From June 250)
The Martyrdom of Alban - Bede, Historia Ecclesiastica Gentis Anglorum, 1.7
The Martyrdom of Polycarp - The Encyclical Epistle of the Church at Smyrna (1-22)
The Passion of Perpetua - (Complete Greek and Latin Text)
Pliny's Letter to Trajan about how to deal with Christians (Letter 10.96 in Loeb 1915 edition)
Tacitus - Persecution under Nero (Annales ab excessu divi Augusti, 15.44)
Tertullian - The Blood of Christians is Seed (Apologeticus pro Christianis (Apology), 48 - 50)
Trajan's Reply to Pliny (Letter 10.97 in Loeb 1915 edition)



Scripture
Athanasius - 39th Festal Letter
Augustine - De Utilitate Credendi (On The Profit of Believing), 3.9
Augustine - on the Septuagint from De Civitate Dei 18. 41-43
Barnabas, Epistle of, 9.6-9 and 12.1-7
Eusebius - The Canon of the New Testament - Historia Ecclesiastica, 3.25
Eusebius - The Canonical Epistles - Historia Ecclesiastica, 3.3
Eusebius - Letter to Carpianus - about the Eusebian canon tables
Eusebius - Origen and OT Text - Historia Ecclesiastica, 6.16
Jerome -A guide is needed to understand Scripture - Letter 53 to Paulinus (4-7 and 10)
Jerome - Latin Bible - Praefatio Hieronymi in Quatuor Evangelia
Jerome - Prefaces to his translations of the Psalms from the Greek and the Hebrew
Jerome - Preface to the Books of Samuel and Kings (Helmeted)
Marcion's rejection of the Old Testament - Irenaeus, Adversus Haereses, 1.24
The Muratorian Canon
Origen - The Harmony of Scripture - Fragment on Matthew from The Philocalia
Origen - Parabolic Element in Scripture - De Principiis, 4. 16
Origen - Understanding Scripture - De Principiis, 4. 11-13

 

Slavery
Gregory of Nyssa - On Slavery - Expositio in Ecclesiasten - beginning of Homily IV



Tradition
Irenaeus - The Rule of Faith - Adversus Haereses, 1.2-3
Irenaeus - On Tradition - Adversus Haereses, 3.2.1 - 3.4.2
Tertullian - On Tradition - De Praescriptione Haereticorum, 20, 21 and 32



The Trinity
Athanasius - Tomus ad Antiochenos, 3 - 7
Augustine on the Trinity - De Trinitate, 9.1-5
Basil - Ousia and Hypostasis - Letter, 236.6
Dionysius of Alexandria - From Athanasius, De Sententia Dionysii, 14 (end of) - 18
Dionysius of Rome - Letter Against The Sabellians
Gregory of Nazianzus - The Holy Spirit - Oration 31, 9-11, Theological Oration, 5
Hilary of Poitiers - De Trinitate Libri Duodecim, 12.52 and 57
Novatian - De Trinitate, 31
Tertullian - Adversus Praxeam, 2-3
See also under 'Arius' and 'creeds'