Defending and defining the faith (c. 130-451)

What you'll learn

Describe how the Apologists, Irenaeus and Tertullian defended and explained the faith against pagan critics, Gnostics, Marcion and modalists.
Explain how the New Testament canon was recognised over time, and what Constantine and the Council of Nicaea did and did not do.
Summarise what the councils of Nicaea (325), Constantinople (381), Ephesus (431) and Chalcedon (451) confessed, and show why Reformed Christians gladly receive them as faithful to Scripture.

Answering the critics: the Apologists

In the second century Christians were accused of atheism (they rejected the gods), cannibalism (garbled rumours about eating the body and blood of Christ) and incest (they called each other 'brother' and 'sister' and shared a 'love feast'). A group of writers known as the Apologists, from the Greek apologia, 'a reasoned defence' (1 Pet 3:15), answered these charges in public.

The best known is Justin Martyr (c. 100-c. 165), born in Flavia Neapolis in Samaria. He searched through the philosophical schools until an old man he met near the sea pointed him to the Hebrew prophets and to Christ (Dialogue with Trypho 3-8). Around 155 he addressed his First Apology to the emperor Antoninus Pius. He argued that Christians were moral, loyal citizens, that Christ is the eternal Word (Logos) through whom God made all things, and that fulfilled prophecy proves the gospel. He also gives the earliest detailed description of Sunday worship outside the New Testament: 'on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read, as long as time permits' (First Apology 67), followed by preaching, prayer and the Lord's Supper. In his Dialogue with Trypho he argued with a Jewish teacher from the Old Testament. Around 165, under the prefect Junius Rusticus, Justin and six companions were beheaded in Rome for refusing to sacrifice.

Justin shows that apologetics is not a modern invention. He used reason, history and prophecy, and he sealed his witness with his life. Reformed readers will notice that he could be generous towards Greek philosophy (he spoke of 'seeds' of the Word among the philosophers), which later Christians, especially presuppositionalists, have weighed carefully.

What three charges were brought against second-century Christians, and where did each come from?Show answer

They were accused of atheism because they rejected the gods, of cannibalism because of garbled rumours about eating the body and blood of Christ, and of incest because they called each other 'brother' and 'sister' and shared a 'love feast'. The Apologists, named from the Greek apologia, 'a reasoned defence' (1 Pet 3:15), answered these charges in public.

atheism: rejecting the gods
cannibalism: rumours about the Supper
incest: brother/sister, love feast
Apologists answered publicly

Why does Justin Martyr show that apologetics is not a modern invention? Describe how he argued.Show answer

Around 155 Justin addressed his First Apology to the emperor, arguing that Christians were moral, loyal citizens, that Christ is the eternal Word through whom God made all things, and that fulfilled prophecy proves the gospel. In his Dialogue with Trypho he argued from the Old Testament with a Jewish teacher. He used reason, history and prophecy, and he sealed his witness when he was beheaded in Rome around 165.

First Apology to the emperor
Christ the Logos
fulfilled prophecy
died as a martyr

Irenaeus against the Gnostics: the rule of faith

A more dangerous threat came from inside the churches. The Gnostics (from gnosis, 'knowledge') taught that the material world was made by an ignorant lesser god, that salvation means escaping the body through secret knowledge, and that Christ did not truly take flesh. They produced their own gospels; many were rediscovered at Nag Hammadi in Egypt in 1945.

Irenaeus grew up in Smyrna, where as a boy he heard Polycarp preach, and became bishop of Lyons in Gaul after the persecution of 177. Around 180 he wrote Against Heresies (its full title is The Detection and Overthrow of Knowledge Falsely So Called). His argument has three strands. First, the apostles taught publicly, not secretly: 'We have learned from none others the plan of our salvation, than from those through whom the Gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith' (3.1.1). Second, the churches the apostles founded could name their succession of leaders and all taught the same faith, which proved there was no hidden tradition (3.3). Third, the whole church, scattered across the world, confessed the same 'rule of faith' (1.10.1): one God the Creator, one Christ Jesus who became incarnate for our salvation, and the Holy Spirit who spoke by the prophets.

Irenaeus is also the earliest surviving writer to insist that there are exactly four Gospels, writing that 'it is not possible that the Gospels can be either more or fewer in number than they are' (3.11.8). He taught that Christ 'recapitulates' (sums up) humanity, succeeding where Adam failed (Rom 5:12-21).

Roman Catholic and Orthodox writers stress Irenaeus's appeal to succession. Reformed readers stress that for Irenaeus the succession mattered because it guarded the public apostolic teaching now written in Scripture. Both are reading him honestly; the question is which serves which.

What did the Gnostics teach, and why were they a more dangerous threat than the outside critics?Show answer

The Gnostics taught that the material world was made by an ignorant lesser god, that salvation means escaping the body through secret knowledge, and that Christ did not truly take flesh. They were more dangerous because they came from inside the churches and produced their own gospels, offering a rival version of the faith rather than attacking it from outside.

ignorant lesser creator
salvation by secret knowledge
Christ not truly flesh
threat from inside

Summarise Irenaeus's three-strand argument against the Gnostics in your own words.Show answer

First, the apostles taught publicly, not secretly, and that public teaching was handed down in the Scriptures. Second, the churches the apostles founded could name their succession of leaders and all taught the same faith, which proved there was no hidden tradition. Third, the whole church across the world confessed the same rule of faith: one God the Creator, one Christ Jesus incarnate for our salvation, and the Holy Spirit who spoke by the prophets.

public, not secret, teaching
written down in Scripture
succession showed no hidden tradition
one rule of faith everywhere

Tertullian and the vocabulary of the Trinity

Tertullian of Carthage (c. 155-c. 220) was the first major Christian theologian to write in Latin. Sharp and witty, he is remembered for asking, 'What indeed has Athens to do with Jerusalem? What concord is there between the Academy and the Church?' (Prescription against Heretics 7), and for the line about the blood of Christians being seed (Apology 50).

His great contribution came in Against Praxeas (early third century), written against a teacher who said that the Father himself was born and suffered, the view later called modalism. Tertullian gave the Western church its words: trinitas (Trinity) and the formula of one substantia (substance) in three personae (persons). The Greek word trias had already been used by Theophilus of Antioch around 180. These words did not invent a new doctrine; they named what Christians already confessed when they baptised 'in the name of the Father and of the Son and of the Holy Spirit' (Matt 28:19). Later in life Tertullian was drawn to the Montanist movement, which claimed new prophecy, so the church honoured his insights without following him everywhere.

How would you answer someone who says that because Tertullian coined the word 'Trinity', the doctrine was invented in the third century?Show answer

Tertullian, writing against modalism in Against Praxeas, gave the Western church the word trinitas and the formula of one substance in three persons, and Theophilus had already used the Greek trias around 180. But these words named what Christians already confessed when they baptised 'in the name of the Father and of the Son and of the Holy Spirit' (Matt 28:19). A new word is not a new doctrine; it is a precise label for an existing belief.

Against Praxeas, against modalism
one substance, three persons
already confessed at baptism (Matt 28:19)
words named, not invented

Marcion and the recognition of the canon

Marcion (c. 85-c. 160), a wealthy shipowner from Sinope, came to Rome and was excommunicated around 144. He taught that the God of the Old Testament was a lower, harsh creator, different from the loving Father revealed by Jesus. So he rejected the Old Testament and published his own 'canon': an edited Gospel of Luke and ten letters of Paul, cut to fit his theology. Marcion's challenge pushed the churches to say clearly which books they had always received.

The New Testament canon was not decided at one moment. It was recognised over time. The church inherited the Old Testament from Israel and Jesus (Luke 24:44). Already within the New Testament, Paul's letters are counted among 'the other Scriptures' (2 Pet 3:15-16), and 1 Timothy 5:18 quotes words found in Luke 10:7 alongside Deuteronomy as 'Scripture'. By the late second century the four Gospels, Acts and thirteen letters of Paul were widely accepted (Irenaeus; the Muratorian fragment, probably late second century, though some date it to the fourth). A handful of books were debated for longer. Eusebius, writing in the early fourth century, lists James, Jude, 2 Peter and 2 and 3 John as 'disputed' though recognised by many, and Revelation as accepted by some and rejected by others.

In 367 Athanasius of Alexandria, in his 39th Festal Letter, listed exactly our 27 books, saying: 'These are fountains of salvation, that they who thirst may be satisfied with the living words they contain. In these alone is proclaimed the doctrine of godliness. Let no man add to these, neither let him take ought from these.' North African synods at Hippo (393) and Carthage (397) recognised the same 27 New Testament books. (Their Old Testament lists included the books Protestants call the Apocrypha, a point Catholic apologists rightly raise; that question returns with Jerome in the next lesson.)

The Reformed position is that the church did not give the books their authority; it received books that carried God's authority in themselves (WCF 1.4-5). As Michael Kruger puts it, the canon is self-authenticating, and the church's agreement is the result, not the cause, of its authority. (You met this in Know Your Faith, Lesson 1; The Reliable Word, Lesson 2, takes the canon further.)

What did Marcion teach, and how did his challenge affect the church?Show answer

Marcion taught that the God of the Old Testament was a lower, harsh creator, different from the loving Father revealed by Jesus. He rejected the Old Testament and published his own 'canon' of an edited Luke and ten letters of Paul, cut to fit his theology. His challenge pushed the churches to say clearly which books they had always received.

two different gods
rejected the Old Testament
edited Luke and ten Pauline letters
pushed churches to name their books

What is the difference between saying the church 'decided' the canon and saying it 'recognised' the canon? Use evidence from the section.Show answer

'Decided' implies the books got their authority from the church; 'recognised' means the church acknowledged books that already carried God's authority. The evidence fits recognition: within the New Testament, Paul's letters are counted with 'the other Scriptures' (2 Pet 3:15-16), the core books were widely accepted by the late second century, and later lists like Athanasius's in 367 confirmed what had been received. The Reformed view (WCF 1.4-5) is that the church's agreement is the result, not the cause, of the books' authority.

authority lies in the books
2 Pet 3:15-16 and 1 Tim 5:18
gradual consensus, Athanasius 367
agreement is result, not cause

Constantine: what he did and did not do

On 28 October 312 Constantine defeated Maxentius at the Milvian Bridge outside Rome. Lactantius, writing soon after, says he was told in a dream to mark a Christian sign on his soldiers' shields; Eusebius, writing decades later, adds a vision of a cross of light with the words 'By this conquer'. From then on Constantine favoured the church: he agreed religious freedom with Licinius in 313, funded great basilicas, gave clergy exemptions, made Sunday a day of rest (321), and around 331 ordered fifty copies of the Scriptures from Eusebius for the churches of Constantinople (Life of Constantine 4.36). He also kept the old pagan title pontifex maximus and was baptised only on his deathbed in May 337, by Eusebius of Nicomedia, a sympathiser of Arius.

What he did not do matters just as much for apologetics. He did not make Christianity the state religion (that was Theodosius's Edict of Thessalonica in 380). He did not vote at Nicaea, because he was not a bishop. He did not invent the deity of Christ, which Christians had confessed for nearly three centuries. And he did not choose the books of the Bible. There is no record that the canon was discussed at Nicaea at all. The popular story of books being placed on an altar, with the false ones falling to the floor, comes from a much later Byzantine text (the ninth-century Synodicon Vetus) and was spread by Voltaire; The Da Vinci Code (2003) gave new life to the broader claim that Constantine picked the books.

Example: Answering the Nicaea myth at a barbecue

Friend: Didn't Constantine pick the books of the Bible at Nicaea? I read that somewhere.

You: It's a common story, so it's worth checking. What do you think the council met to discuss?

Friend: The Bible, I assume. And whether Jesus was God.

You: The question in 325 was whether the Son is eternal God or, as Arius taught, the first and greatest creature. There's no record that the council discussed which books belong in the Bible at all. The story of books on an altar comes from a Byzantine text written centuries later.

Friend: So where did the list come from?

You: It was recognised over time. Paul's letters are already called Scripture in 2 Peter 3:16, and by about 180 Irenaeus treats the four Gospels as fixed. The first list of exactly our 27 books is Athanasius's letter of 367, more than forty years after Nicaea.

Friend: But Constantine still pushed the idea that Jesus was God.

You: Christians were worshipping Jesus long before him. Around 112 a Roman governor, Pliny, reported them singing 'to Christ as to a god'. And after Nicaea, Constantine actually favoured Arius's supporters. The deity of Christ survived in spite of emperors, not because of them.

Friend: Huh. I didn't know that.

You: Here's the bigger question, though. If Jesus really is who those first Christians said he is, what would that mean for you?

List some things Constantine actually did for the church, and some signs that his Christianity was mixed.Show answer

He agreed religious freedom with Licinius in 313, funded great basilicas, gave clergy exemptions, made Sunday a day of rest in 321, and ordered fifty copies of the Scriptures for the churches of Constantinople. Yet he kept the pagan title pontifex maximus and was baptised only on his deathbed in 337, by Eusebius of Nicomedia, a sympathiser of Arius.

religious freedom 313
basilicas, Sunday rest, Bible copies
kept pontifex maximus
deathbed baptism by Arian sympathiser

How would you answer a friend who has heard that Constantine chose the books of the Bible at Nicaea?Show answer

There is no record that the canon was discussed at Nicaea at all, and Constantine did not vote there because he was not a bishop. The story of books being placed on an altar, with the false ones falling to the floor, comes from a ninth-century Byzantine text and was spread by Voltaire; The Da Vinci Code revived the broader claim. It is a popular story, not history.

no record canon was discussed
Constantine had no vote
altar story is ninth-century
spread by Voltaire and Da Vinci Code

Nicaea (325), Arius and Athanasius

Around 318 Arius, a popular presbyter in Alexandria, began teaching that the Son was the first and greatest creature: 'there was a time when he was not'. His bishop Alexander, assisted by a young deacon named Athanasius, opposed him. The quarrel spread, and Constantine called a council at Nicaea in Asia Minor (May to July 325). About 250-300 bishops attended, almost all from the East; later tradition fixed the number at 318. Constantine opened the council and paid the costs; Hosius of Cordoba probably presided for him.

The bishops searched the Scriptures, but they found that Arians could agree to every biblical phrase while emptying it of meaning. So they chose a word that Arians could not accept: the Son is homoousios, 'of one substance', with the Father. (You met homoousios in Know Your Faith, Lesson 3.) The creed confessed the Son as 'God of God, Light of Light, very God of very God, begotten, not made', and anathematised anyone who said 'there was a time when the Son of God was not'. All but two bishops signed. The council also fixed a common method for dating Easter and issued about twenty canons on church order.

Nicaea did not end the controversy. For the next half century Arian and semi-Arian parties often had imperial support, including from Constantine himself in his later years and from his son Constantius II. At the Council of Ariminum (359) the Western bishops were pressured into an ambiguous creed, and Jerome later remarked that the world groaned to find itself Arian. Athanasius (c. 296-373), bishop of Alexandria from 328, was exiled five times, for about seventeen years in all, for refusing to compromise. His On the Incarnation explains why only one who is truly God can save us. If emperors were dictating doctrine, the deity of Christ would have lost; it survived because bishops like Athanasius would not let go of what Scripture teaches (John 1:1-3; 20:28; Heb 1:3, 8).

Why did the bishops at Nicaea use a word that is not in the Bible, homoousios?Show answer

Arius taught that the Son was the first and greatest creature: 'there was a time when he was not'. The bishops found that Arians could agree to every biblical phrase while emptying it of meaning. So they chose a word Arians could not accept, homoousios, 'of one substance' with the Father, to pin down what Scripture means about the Son.

Arius: Son a creature
Arians accepted biblical phrases but emptied them
homoousios: 'of one substance'
protects the biblical meaning

Why does the story of Athanasius undermine the claim that emperors dictated Christian doctrine?Show answer

After Nicaea, Arian and semi-Arian parties often had imperial support, including Constantine in his later years and his son Constantius II, and Western bishops were pressured into an ambiguous creed at Ariminum in 359. Athanasius was exiled five times, about seventeen years in all, for refusing to compromise. If emperors had been dictating doctrine, the deity of Christ would have lost; it survived because bishops would not let go of what Scripture teaches.

emperors often backed Arians
Ariminum 359
Athanasius exiled five times
doctrine survived despite power

Constantinople, Ephesus and Chalcedon

Constantinople (381). Under Theodosius I, about 150 Eastern bishops met in Constantinople. Building on the work of the Cappadocian Fathers (Basil of Caesarea, Gregory of Nazianzus and Gregory of Nyssa), they reaffirmed Nicaea and confessed the full deity of the Holy Spirit against those who denied it, as well as rejecting Apollinarius, who denied that Christ had a human mind. The expanded creed associated with this council, confessing the Spirit as 'the Lord and Giver of life', is what most churches today call the Nicene Creed.

Ephesus (431). Nestorius, bishop of Constantinople, objected to calling Mary Theotokos, 'God-bearer', preferring 'Christ-bearer'. Cyril of Alexandria answered that the one born of Mary is the eternal Son in the flesh, so the title protects the unity of Christ's person. The council deposed Nestorius. The title was first of all a statement about Jesus, not an exaltation of Mary. The council also condemned Pelagian teaching. The Church of the East, in the Persian Empire, did not accept the council's condemnation of Nestorius and went its own way; it was later labelled 'Nestorian', a name it rejects.

Chalcedon (451). The monk Eutyches swung to the opposite error, blurring Christ's two natures into one. Called by the emperor Marcian, about 520 bishops met at Chalcedon, read Pope Leo's Tome, and produced the Definition: one Christ 'in two natures, inconfusedly, unchangeably, indivisibly, inseparably'. These four negatives fence off the errors on each side (mixture and division) without claiming to explain the mystery. (You studied the Definition in Know Your Faith, Lesson 4.) The Oriental Orthodox churches (Coptic, Ethiopian, Armenian, Syriac) did not accept Chalcedon, and many today describe their view as miaphysite rather than Eutychian.

Why it matters. The Reformers did not reject these councils. Calvin wrote that he willingly embraced and reverenced as sacred the early councils of Nicaea, Constantinople, the first of Ephesus and Chalcedon, so far as their doctrines of faith are concerned, because they contain nothing but the pure and genuine interpretation of Scripture (Institutes 4.9.8), while insisting that councils can err and must be tested by Scripture (WCF 31.3; 31.4 in the original 1646 text). The Westminster Confession's statement on Christ (8.2) deliberately echoes Chalcedon. When someone says 'the church invented the Trinity in the fourth century', the answer is that the councils defined, in careful words, what Scripture already taught and Christians already worshipped, much as the apostles and elders did in Acts 15.

Explain briefly what the councils of Constantinople (381), Ephesus (431) and Chalcedon (451) each clarified.Show answer

Constantinople reaffirmed Nicaea, confessed the full deity of the Holy Spirit and rejected Apollinarius's denial of Christ's human mind; its expanded creed is what most churches call the Nicene Creed. Ephesus deposed Nestorius and upheld the title Theotokos to protect the unity of Christ's person. Chalcedon confessed one Christ in two natures 'inconfusedly, unchangeably, indivisibly, inseparably', fencing off both mixture and division.

381: deity of the Spirit
431: unity of Christ's person
451: two natures, one Christ
four negatives fence off errors

What was the Reformers' attitude to these early councils, and how does it help answer the claim that 'the church invented the Trinity in the fourth century'?Show answer

The Reformers embraced them: Calvin reverenced Nicaea, Constantinople, Ephesus and Chalcedon as containing the genuine interpretation of Scripture, while insisting that councils can err and must be tested by Scripture (WCF 31). So the answer is that the councils defined, in careful words, what Scripture already taught and Christians already worshipped, much as the apostles and elders did in Acts 15.

Calvin embraced the four councils
councils can err, tested by Scripture
defined, not invented
like Acts 15

Key texts

1 Peter 3:15: The charter of apologetics: be ready to give a reasoned defence (apologia) for the hope within you. The Apologists took their name from this word.
Jude 3: Contend for the faith once for all delivered to the saints: the conviction behind Irenaeus's rule of faith and Athanasius's stand.
2 Peter 3:15-16: Paul's letters are already placed among 'the other Scriptures': the canon recognised within the New Testament itself.
1 Timothy 5:18: Paul quotes Deuteronomy 25:4 and words found in Luke 10:7 together as 'Scripture'.
John 1:1-3: The Word was God and made all things, so he is not one of the things made: the text that answers Arius.
Colossians 2:8-9: Beware of empty philosophy; in Christ the whole fullness of deity dwells bodily. Speaks to both Gnostic speculation and the two natures of Christ.
1 John 4:2-3: Every spirit that confesses Jesus Christ has come in the flesh is from God: the apostolic answer to Gnostic denial of the incarnation.
Acts 15:6-29: The apostles and elders meet, argue from Scripture and reach a common judgement: the pattern later councils followed, under Scripture's authority.

Objections and answers

Try answering each one yourself before you open the response.

“The Bible was put together at the Council of Nicaea, when Constantine chose the books that suited him.”Show a response

That is a popular claim, but there is no record that Nicaea discussed the canon at all. The story of books placed on an altar comes from a Byzantine text written centuries later and was popularised by Voltaire; The Da Vinci Code revived the wider idea that Constantine chose the books. The real history is slower and more interesting. Paul's letters are already called Scripture in 2 Peter 3:16. By about 180 Irenaeus treats the four Gospels as fixed. The Muratorian fragment lists most of our New Testament. A few books, like 2 Peter and Jude, were debated longer. Athanasius gives our exact 27 books in 367, more than forty years after Nicaea. The churches recognised the books that had been read and trusted from the beginning. No emperor chose them.

“Constantine invented the divinity of Jesus at Nicaea to unify his empire.”Show a response

The evidence runs the other way. Long before Constantine, Pliny reported around 112 that Christians sang hymns to Christ 'as to a god', and Ignatius around 110 called Jesus 'our God'. The New Testament itself calls him God (John 1:1; 20:28; Titus 2:13). At Nicaea the question was not whether Jesus was divine, but whether Arius's view, that the Son was a created being, fitted Scripture. Constantine did not vote, since he was not a bishop. And notice what happened next: Constantine later favoured Arius's sympathisers, his son Constantius backed the Arian side, and Athanasius was exiled five times. If emperors were deciding doctrine, Arianism would have won. The Nicene faith survived because it was the faith of Scripture.

“Your doctrines evolved over centuries through politics and councils. Why trust fourth-century bishops?”Show a response

We do not trust them as a final authority. Reformed churches say councils can err and must be tested by Scripture (WCF 31.3). But we test them and find that the great councils got it right. They did not add new beliefs; they found precise words to guard old ones against new denials, as the apostles and elders did in Acts 15. Christians baptised in the triune name from the start (Matt 28:19) and worshipped Jesus from the start (Phil 2:9-11). Nicaea's word homoousios simply says what John 1:1 says. Doctrine developed in clarity of expression, not in substance. Think of a scientific term coined to describe something that was always there: the word is new, the reality is not.

“The Gnostic gospels were suppressed by the side that won. They're just as authentic as Matthew, Mark, Luke and John.”Show a response

The Gnostic texts rediscovered at Nag Hammadi in 1945 are genuinely interesting, and it's worth reading them. But the early church did not set them aside simply because it was the stronger party; it set them aside because they taught a different faith. The Gnostics said the material world was made by an ignorant lesser god, that Christ did not truly take flesh, and that salvation comes through secret knowledge. Irenaeus answered around 180 that the apostles taught publicly, not secretly, and that the churches they founded all confessed the same faith. He already insisted there were exactly four Gospels, and most scholars date the Gnostic gospels later than those four. The church was not inventing a list to suit itself; it was recognising which writings carried the apostles' teaching (2 Pet 3:15-16).

“Words like 'Trinity', 'substance' and 'person' aren't in the Bible. Christianity got hijacked by Greek philosophy.”Show a response

It's a fair question, and the early church felt it too: Tertullian, who gave us the word 'Trinity', famously asked what Athens has to do with Jerusalem. But using a word is not the same as adopting a philosophy. At Nicaea the bishops searched the Scriptures and found that Arius's followers could agree to every biblical phrase while emptying it of meaning. So they chose homoousios, 'of one substance', precisely to protect what Scripture says about the Son (John 1:1-3; Heb 1:3). These words named what Christians already confessed when they baptised in the one name of the Father, the Son and the Holy Spirit (Matt 28:19). And Chalcedon's four negatives don't explain the mystery away; they simply fence off errors on either side. The goal was faithfulness to Scripture, not speculation.

Written task

A Year 11 student tells you he watched a video claiming that 'the Emperor Constantine decided which books went into the Bible and voted Jesus into being God at Nicaea.' Write a 300-400 word explanation suitable for a thoughtful teenager. Separate what Constantine actually did from what he did not do, explain how the New Testament canon was recognised (with at least two primary sources and dates), and explain what Nicaea actually decided and why. Use at least two Scripture references.

Hand this in to Mr Scott. He will look for:

Accurately separates Constantine's real actions from the myths
Explains canon recognition with at least two dated primary sources (e.g. Irenaeus c. 180, Athanasius 367)
Explains Arius's view and the meaning of homoousios correctly
Uses at least two relevant Scripture references
Clear, respectful tone suited to a teenager