I’m answering a question often asked of me by atheists – What would move a strong atheist to become a strong theist? In my case the answer was evidence for theism, specifically for Christian theism.

We started sharing the evidence that can lead an atheist to theism and Christianity several years ago (click here to read the first article in this series). We’ve most recently been looking at evidence for the reliability of the New Testament writings.

So far we’ve looked at –

We move now to external evidence for Luke’s authorship of the Book of Acts.

[Just a reminder that we’re only revealing the evidence available in the early part of 1971 during my investigation. A future series will look at evidence that has been discovered since that time.]

Here is a basic investigative process for determining ancient authorship:

  • Internal evidence – what we find in the letter itself .. claim of authorship, historical information, geographical information, biographical information.
  • Language and style – comparing writing style of other letters believed to have been written by same author (e.g. vocabulary, sentence structure, grammar, idioms).
  • Content – comparing the content with other letters believed to have been written by same author (e.g. theology, historical data).
  • External evidence – ancient writers supporting claim of authorship, ancient writers quoting from writings in question, archaeological evidence supporting authorship and/or accuracy of information contained in original writing.

External Evidence

As we have seen in this series and others published in Faith and Self Defense, some of the earliest external evidence comes from the Apostolic Fathers. Those were men who knew some of the apostles of Christ personally and were early leaders in the Church. Those include Clement of Rome, Ignatius of Antioch, Polycarp of Smyrna, and Papias of Hierapolis. Their writings spanned the latter part of the 1st century AD into the early part of the 2nd century AD. We learn much about the beliefs and practices of early Christians during those early years.

First Clement

Clement was a first century bishop of Rome who knew the Apostles Paul personally and may have also known Peter and other apostles as well. He wrote a letter to the church in Corinth toward the end of the first century to address some concerns. Clement quoted from almost half of the writings in the New Testament in that letter, which demonstrates that those writings were both available to the early Church and carried Apostolic authority when quoted.

Clement quoted from portions of Luke’s Gospel (in chapters 6, 8 and 17) and may have also quoted from Acts –

I have shown you in every way, by laboring like this, that you must support the weak. And remember the words of the Lord Jesus, that He said, ‘It is more blessed to give than to receive.’

Acts 20:35

And ye were all lowly in mind and free from arrogance, yielding rather than claiming submission, more glad to give than to receive, and content with the provisions which God supplieth. And giving heed unto His words, ye laid them up diligently in your hearts, and His sufferings were before your eyes.

1 Clement 2:1, Translated by J.B. Lightfoot

Ignatius to the Magnesians

Ignatius was a first century and early second century bishop of Antioch, Syria, who knew the Apostle John. Ignatius lived a long life and wrote several famous letters on his way to martyrdom in Rome.

  • To Polycarp
  • To the Smyraeans
  • To the Philadelphians
  • To the Romans
  • To the Trallians
  • To the Magnesians
  • To the Ephesians

Ignatius quoted from several writings in the New Testament including Acts –

… to take part in this ministry and apostleship from which Judas by transgression fell, that he might go to his own place.

Acts 1:25

Seeing them that all things have an end, and these two — life and death — are set before us together, and each man shall go _to his own place.

Magnesians 5:1, Translated by J.B. Lightfoot

Polycarp To the Philippians

Polycarp was born about 69 AD and served as bishop of Smyrna until his death in 155 AD. Polycarp was a disciple of the Apostle John, who may have ordained him to be the bishop. We are left with only one letter from Polycarp, his Letter to the Philippians. He quoted from about 17 of the apostles’ writings in the letter, including from Acts.

… whom God raised up, having loosed the pains of death, because it was not possible that He should be held by it.

Acts 2:24

… and that the steadfast root of your faith which was famed from primitive times abideth until now and beareth fruit unto our Lord Jesus Christ, who endured to face even death for our sins, whom God raised, having loosed the pangs of Hades.

Polycarp 1:2, Translated by J.B. Lightfoot

And He commanded us to preach to the people, and to testify that it is He who was ordained by God to be Judge of the living and the dead.

Acts 10:42

Wherefore gird up your loins and serve God in fear and truth, forsaking the vain and empty talking and the error of the many, for that ye have believed on Him that raised our Lord Jesus Christ from the dead and gave unto him glory and a throne on His right hand; unto whom all things were made subject that are in heaven and that are on the earth; to whom every creature that hath breath doeth service; who cometh as judge of quick and dead; whose blood God will require of them that are disobedient unto Him.

Polycarp 2:1, Translated by J.B. Lightfoot

Papias Fragments

Papias was born about 60 AD and died about 130 AD. He was a bishop of Hierapolis and may have been a disciple of the Apostle John and friend of Polycarp. Papias wrote The Exposition of the Oracles of the Lord in five books, but only fragments of what he wrote in those books are available for us to study. Those fragments come to us from the writings of Irenaeus (a second century bishop of Smyrna who served with Polycarp) and Church historian Eusebius (early 4th century bishop of Caesarea Maritima).

The fragments we have show that Papias was familiar with several Apostolic writings (e.g. Matthew, Mark, Luke, John, 1st John) and had also spoken with people who had learned from the apostles (e.g. Peter, Andrew). It’s also possible he was a personal learner of John.

As for the Book of Acts, one fragment mentions Justus Barsabas (mentioned in Acts 1:23 and 15:22). Another gives an account of the death of Judas Iscariot which may have been for the purpose of reconciling the story in Matthew’s Gospel with the account in the Book of Acts.

Other Early Church Fathers

We can also look to other early Church Fathers to see what New Testament writings they used as authoritative. Here are some examples.


Irenaeus was a second century bishop of Lyons (city in ancient Gaul) who had sat under the teaching ministry of Polycarp of Smyrna. Irenaeus grew up in or near Smyrna and later traveled to Lyons when Polycarp sent Pothinus to evangelize the area and establish local churches. Irenaeus became bishop of Lyons upon the martyrdom of Pothinus.

We have some of the writings of Irenaeus to read today. They are known as Against Heresies (On the Detection and Overthrow of the So-Called Gnosis) and are available in five books. We also have an Armenian translation of The Demonstration of the Apostolic Teaching. Irenaeus quoted from most of the Apostolic writings in his writings, including the Book of Acts. Here are two examples.

But there was a certain man called Simon, who previously practiced sorcery in the city and astonished the people of Samaria, claiming that he was someone great, to whom they all gave heed, from the least to the greatest, saying, ‘This man is the great power of God.’ And they heeded him because he had astonished them with his sorceries for a long time. But when they believed Philip as he preached the things concerning the kingdom of God and the name of Jesus Christ, both men and women were baptized. Then Simon himself also believed; and when he was baptized he continued with Philip, and was amazed, seeing the miracles and signs which were done … And when Simon saw that through the laying on of the apostles’ hands the Holy Spirit was given, he offered them money, saying, ‘Give me this power also, that anyone on whom I lay hands may receive the Holy Spirit.’ But Peter said to him, ‘Your money perish with you, because you thought that the gift of God could be purchased with money! You have neither part nor portion in this matter, for your heart is not right in the sight of God. Repent therefore of this your wickedness, and pray God if perhaps the thought of your heart may be forgiven you. For I see that you are poisoned by bitterness and bound by iniquity.’ Then Simon answered and said, ‘Pray to the Lord for me, that none of the things which you have spoken may come upon me.

Acts 8:9-13, 18-24

Simon the Samaritan was that magician of whom Luke, the disciple and follower of the apostles, says, ‘But there was a certain man, Simon by name, who beforetime used magical arts in that city, and led astray the people of Samaria, declaring that he himself was some great one, to whom they all gave heed, from the least to the greatest, saying, This is the power of God, which is called great. And to him they had regard, because that of long time he had driven them mad by his sorceries.’ This Simon, then-who feigned faith, supposing that the apostles themselves performed their cures by the art of magic, and not by the power of God; and with respect to their filling with the Holy Ghost, through the imposition of hands, those that believed in God through Him who was preached by them, namely, Christ Jesus-suspecting that even this was done through a kind of greater knowledge of magic, and offering money to the apostles, thought he, too, might receive this power of bestowing the Holy Spirit on whomsoever he would,-was addressed in these words by Peter: ‘Thy money perish with thee, because thou hast thought that the gift of God can be purchased with money: thou hast neither part nor lot in this matter, for thy heart is not fight in the sight of God; for I perceive that thou art in the gall of bitterness, and in the bond of iniquity.’ He, then, not putting faith in God a whit the more, set himself eagerly to contend against the apostles, in order that he himself might seem to be a wonderful being, and applied himself with still greater zeal to the study of the whole magic art, that he might the better bewilder and overpower multitudes of men. Such was his procedure in the reign of Claudius Caesar, by whom also he is said to have been honoured with a statue, on account of his magical power. This man, then, was glorified by many as if he were a god; and he taught that it was himself who appeared among the Jews as the Son, but descended in Samaria as the Father while he came to other nations in the character of the Holy Spirit. He represented himself, in a word, as being the loftiest of all powers, that is, the Being who is the Father over all, and he allowed himself to be called by whatsoever title men were pleased to address him.

Against Heresies, Book I, Chapter 23.1

Now an angel of the Lord spoke to Philip, saying, ‘Arise and go toward the south along the road which goes down from Jerusalem to Gaza.’ This is desert. So he arose and went. And behold, a man of Ethiopia, a eunuch of great authority under Candace the queen of the Ethiopians, who had charge of all her treasury, and had come to Jerusalem to worship, was returning. And sitting in his chariot, he was reading Isaiah the prophet. Then the Spirit said to Philip, ‘Go near and overtake this chariot.’ So Philip ran to him, and heard him reading the prophet Isaiah, and said, ‘Do you understand what you are reading?’ And he said, ‘How can I, unless someone guides me?’ And he asked Philip to come up and sit with him. The place in the Scripture which he read was this: ‘He was led as a sheep to the slaughter; And as a lamb before its shearer is silent, So He opened not His mouth. In His humiliation His justice was taken away, And who will declare His generation? For His life is taken from the earth.’ So the eunuch answered Philip and said, ‘I ask you, of whom does the prophet say this, of himself or of some other man?’ Then Philip opened his mouth, and beginning at this Scripture, preached Jesus to him. Now as they went down the road, they came to some water. And the eunuch said, ‘See, here is water. What hinders me from being baptized?’ Then Philip said, ‘If you believe with all your heart, you may.’ And he answered and said, “I believe that Jesus Christ is the Son of God.’ So he commanded the chariot to stand still. And both Philip and the eunuch went down into the water, and he baptized him. Now when they came up out of the water, the Spirit of the Lord caught Philip away, so that the eunuch saw him no more; and he went on his way rejoicing.

Acts 8:26-39

But again: Whom did Philip preach to the eunuch of the queen of the Ethiopians, returning from Jerusalem, and reading Esaias the prophet, when he and this man were alone together? Was it not He of whom the prophet spoke: “He was led as a sheep to the slaughter, and as a lamb dumb before the shearer, so He opened not the month? “”But who shall declare His nativity? for His life shall be taken away from the earth.” [Philip declared] that this was Jesus, and that the Scripture was fulfilled in Him; as did also the believing eunuch himself: and, immediately requesting to be baptized, he said, “I believe Jesus Christ to be the Son of God.” This man was also sent into the regions of Ethiopia, to preach what he had himself believed, that there was one God preached by the prophets, but that the Son of this [God] had already made [His] appearance in human nature (secundum hominem), and had been led as a sheep to the slaughter; and all the other statements which the prophets made regarding Him.

Against Heresies, Book III, Chapter 12.8

Clement of Alexandria

Clement of Alexandria was a philosopher and Christian theologian in the latter part of the 2nd century AD and early part of the 3rd century AD. He wrote several books and quoted from most of the Apostolic writings, including Acts. Here are two examples.

The next day, as they went on their journey and drew near the city, Peter went up on the housetop to pray, about the sixth hour. Then he became very hungry and wanted to eat; but while they made ready, he fell into a trance and saw heaven opened and an object like a great sheet bound at the four corners, descending to him and let down to the earth. In it were all kinds of four-footed animals of the earth, wild beasts, creeping things, and birds of the air. And a voice came to him, ‘Rise, Peter; kill and eat.’ But Peter said, ‘Not so, Lord! For I have never eaten anything common or unclean.’ And a voice spoke to him again the second time, ‘What God has cleansed you must not call common.’ This was done three times. And the object was taken up into heaven again.

Acts 10:9-16

Peter abstained from swine; ‘but a trance fell on him,’ as is written in the Acts of the Apostles, ‘and he saw heaven opened, and a vessel let down on the earth by the four corners, and all the four-looted beasts and creeping things of the earth and the fowls of heaven in it; and there came a voice to him, Rise, and slay, and eat. And Peter said, Not so, Lord, for I have never eaten what is common or unclean. And the voice came again to him the second time, What God hath cleansed, call not thou common. 

The Instructor, Book II, Chapter 1

Then Paul stood in the midst of the Areopagus and said, ‘Men of Athens, I perceive that in all things you are very religious; for as I was passing through and considering the objects of your worship, I even found an altar with this inscription: TO THE UNKNOWN GOD.Therefore, the One whom you worship without knowing, Him I proclaim to you: God, who made the world and everything in it, since He is Lord of heaven and earth, does not dwell in temples made with hands. Nor is He worshiped with men’s hands, as though He needed anything, since He gives to all life, breath, and all things. And He has made from one blood every nation of men to dwell on all the face of the earth, and has determined their preappointed times and the boundaries of their dwellings, so that they should seek the Lord, in the hope that they might grope for Him and find Him, though He is not far from each one of us; for in Him we live and move and have our being, as also some of your own poets have said, ‘For we are also His offspring.’Therefore, since we are the offspring of God, we ought not to think that the Divine Nature is like gold or silver or stone, something shaped by art and man’s devising. Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent, because He has appointed a day on which He will judge the world in righteousness by the Man whom He has ordained. He has given assurance of this to all by raising Him from the dead.

Acts 17:22-31

Paul, in the Acts of the Apostles, is recorded to have said to the Areopagites, ‘I perceive that ye are more than ordinarily religious. For as I passed by, and beheld your devotions, I found an altar with the inscription, To The Unknown God. Whom therefore ye ignorantly worship, Him declare I unto you. God, that made the world and all things therein, seeing that He is Lord of heaven and earth, dwelleth not in temples made with hands; neither is worshipped with men’s hands, as though He needed anything, seeing He giveth to all life, and breath, and all things; and hath made of one blood all nations of men to dwell on all the face of the earth, and hath determined the times before appointed, and the bounds of their habitation; that they should seek God, if haply they might feel after Him, and find Him; though He be not far from every one of us: for in Him we live, and move, and have our being; as certain also of your own poets have said, For we also are His offspring.

The Stromata, Book I, Chapter 19

Tertullian of Carthage

Tertullian was a Christian author and church leader in the latter part of the 2nd century AD and first part of the 3rd century AD. He quoted from most of the Apostolic writings, including Acts. Here are two examples.

He then cursorily touches on his own conversion from a persecutor to an apostle–confirming thereby the Acts of the Apostles, in which book may be found the very subject of this epistle, how that certain persons interposed, and said that men ought to be circumcised, and that the law of Moses was to be observed; and how the apostles, when consulted, determined, by the authority of the Holy Ghost, that “a yoke should not be put upon men’s necks which their fathers even had not been able to bear.” Now, since the Acts of the Apostles thus agree with Paul, it becomes apparent why you reject them. It is because they declare no other God than the Creator, and prove Christ to belong to no other God than the Creator; whilst the promise of the Holy Ghost is shown to have been fulfilled in no other document than the Acts of the Apostles. Now, it is not very likely that these should be found in agreement with the apostle, on the one hand, when they described his career in accordance with his own statement; but should, on the other hand, be at variance with him when they announce the (attribute of) divinity in the Creator’s Christ–as if Paul did not follow the preaching of the apostles when he received from them the prescription of not teaching the Law.

The Five Books Against Marcion, Book V, Chapter 2

Read Acts 15; 21 and Galatians 2 for comparison to the next Acts quote from Tertullian.

But with regard to the countenance of Peter and the rest of the apostles, he tells us s that ‘fourteen years after he went up to Jerusalem,’ in order to confer with them about the rule which he followed in his gospel, lest perchance he should all those years have been running, and be running still, in vain, (which would be the case,) of course, if his preaching of the gospel fell short of their method. So great had been his desire to be approved and supported by those whom you wish on all occasions to be understood as in alliance with Judaism! When indeed he says, that ‘neither was Titus circumcised,’ he for the first time shows us that circumcision was the only question connected with the maintenance of the law, which had been as yet agitated by those whom he therefore calls ‘false brethren unawares brought in’ … Accordingly, the false brethren who were the spies of their Christian liberty must be thwarted in their efforts to bring it under the yoke of their own Judaism before that Paul discovered whether his labour had been in vain, before that those who preceded him in the apostolate gave him their right hands of fellowship, before that he entered on the office of preaching to the Gentiles, according to their arrangement with him. He therefore made some concession, as was necessary, for a time; and this was the reason why he had Timothy circumcised, and the Nazarites introduced into the temple, which incidents are described in the Acts.

The Five Books Against Marcion, Book V, Chapter 3

We could cite more quotes from early Church leaders, but this should be enough to demonstrate that Christians in the 1st, 2nd and 3rd centuries AD recognized the Book of Acts as a genuine Apostolic writing. I took note of that during my investigation as an atheist.

Next Time

In the next part of our report we will look at archaeological external evidence for the Book of Acts as we continue our series, Convince Me There’s A God.

Scripture taken from the New King James Version®. Copyright © 1982 by Thomas Nelson. Used by permission. All rights reserved.

© Faith and Self Defense, 2022