What was Joseph's reaction to the news of Mary's pregnancy?

The answer will depend on whether you follow later “Church Fathers” and medieval myth or read the Bible as a historic document in its original Hebrew and Greek for the Jewish audience it was originally intended for. The Gentile Church after the destruction of Jerusalem in 70 CE interpreted the NT in a way to conform to Hellenistic and semi-pagan culture. This took for granted that demi-gods were the product of gods like Zeus descending on 15 year old virgins and producing demi-gods. 

Dionysus, alleged son of Zeus and Persephone

https://en.wikipedia.org/wiki/List_of_demigods

Jerome was obsessed with virginity and the Virgins of Rome. (Rome would disappear if there were no more Vestal Virgins.) He said both Joseph and Mary were perpetual virgins. He made matters worse with mistranslations from Greek to Latin in his Vulgate NT.

How would a Jew, a believer in Jesus Christ, read the Greek NT?
1. He would understand Hebrew marriage was different from Roman marriage or modern marriage. Genealogy dominated all society among the 12 tribes. That is why the NT starts with Christ’s pedigree and the Hebrew scriptures in their order ends with Chronicles. The Messiah had to be a lineal descendent of David, John 7:42 and as Paul says Romans 1:3.

2. Parents therefore arranged marriages of their young children. When they reached their teens and first maturity the girl and boy could agree and they were ‘betrothed’ by a ceremony of qiddushin or erusin. This meant they were married in the sense that only a divorce ( a ‘get’) could break the bond. (Far different from present day ‘engagement’). The girl still lived at her father’s house until the bridegroom had built a home for her and was ready to assume all duties of its head of household. Then he called for her and the community to celebrate the wedding in a ceremony called nisu’in, the ‘home-coming’ or ‘coming together’ mentioned several times in the NT in Matt 25, Revelation etc.

3. When the NT says Joseph and Mary (Mariam in the Greek) were betrothed it means they were married according to the Hebrew custom. Once the girl/ woman left her father’s home the couple could enjoy their marriage and man became fully her husband. The nisu’in was an extra ceremony. For Joseph it was not normally possible to bring Mariam to Bethlehem, because as the hereditary home of King David it had been destroyed by Herod, who saw all Davidic descendants as enemies to his claim as king under the Romans. The NT says there was ‘no place’ there. Only shepherds were allowed there. Then Herod used the Roman registration decree to get Davidic claimants to register in Bethlehem. It was highly dangerous for Joseph. More so for Mariam who was both old and pregnant, Luke 1:36. God, through an angel, told Joseph ‘not to be afraid to take your wife with you,’ Mt 1:20, because the child was conceived according to God’s plan.

4. Matt ch 1:18 says: (a) they were betrothed, that is married in our sense. (b) Before their ‘coming together’ Mariam was found to be pregnant by God’s grace of his spiritual action. The term ‘coming together’ refers to nisu’in the celebration of the community at the bridegroom’s home. It is used both in Hebrew and Greek secular literature to mean the ceremony of a bridegroom taking his new wife to his home and the community coming together to celebrate it. The next verse has nothing to do with divorce. The Greek word means putting aside, that is putting her in a safe place and avoiding a long journey during pregnancy and possible death by Herod’s men.

5. To create the virgin conception myth, v 25 was distorted or misunderstood by the early Gentile church. It was ripped out of the chronological sequence. They ignored the Jewish and Christian culture.

And he did not know her till she had brought forth her firstborn son.

Read the context. Mariam was already pregnant. Jewish purity law forbade intercourse with a pregnant woman. If this occurred the legalists could say the child was not pure. This was especially important for Joseph and Mariam and any claim to priesthood and royalty of their offspring. Early Christian/Nazarene writings take the same view about forbidding intercourse once the wife is pregnant.

6. Joseph and Mariam would clearly be both shocked and delighted that they were to have a child as they were both in their old age, Luke 1:36, and it was a miracle as was the child Isaac of Abraham and Sarah and many other faithful couple in the Bible. Children in old age is a sign of God’s hand. In Jewish law a woman is considered a virgin before she menstruates. An old woman who is past her menopause is also considered to be a virgin for the purposes of her fulfilling the laws of purity called Niddah described in Leviticus 12 (=Luke 2:22) and Lev 15:19ff.

7. The semi-pagan Roman-instituted church of Constantine wanted nothing to do with the Jews. Medieval followers of Jerome etc confused the NT history with that of Hellenistic deities and hang-ups about virgins because the Greek and especially Hebrew scriptures were forbidden. The Latin Vulgate was gibberish to many priests and their parishioners. Hebrew scrolls were burnt. Translations into local languages were forbidden on pain of death. Ignorance reigned.

8. The Bible is quite clear about the two spheres of begettal. One is that of humans in marriage. Christ explained that a spiritual, second begettal was possible through the Spirit of God, John 3, to Nicodemus. The confusion caused by the pagans who claimed to be Christians has hidden this greatest truth from present-day, would-be followers of the Eternal God. The authentic documents are recorded more fully at "Jesus, James, Joseph and the past and future Temple" N54final version and in the paper version.

How old were Joseph and Mary when they had Jesus?

Was Mary a young girl, barely a teenager, when she had Jesus? That is what many people believe. But that tradition is the result of a thousand years of medieval myths and mixture with pagan Greek ideas about how a god or demi-god should be born. For the Greeks and Romans, demi-gods were born of the intercourse of Zeus/ Jupiter who disguised himself and seduced some young girl. For the truth of the birth of Jesus we must stick to the Bible and understand what Hebrew and Jewish customs were.

Firstly there is a misunderstanding about the the term 'betrothed' in the gospels.

Is it equivalent to modern 'engagement'? Or does it mean marriage?   

Hebrew Marriage

Jews in the first century usually had arranged marriages that were decided between the parents of the young couple when they were still children. The children were often quite young infants when these discussions began to take place. Sometimes the families were helped by an experienced wise person who knew how to make the backgrounds and personalities match for a long term marriage. Personality shows in young infants. Agreement on religious matters is important for family harmony. The children might therefore come from geographically separated communities who held the same beliefs. 

However this was not the primary consideration. That was the longevity of the family line and its adherence to the laws of God. So religious belief and solid character were seen as contributing to this major duty. 

This choice was even more pronounced when it came to two sorts of families: those belonging to the priestly line and those of the royal line. The first had to show real understanding of the instructions that had to be fulfilled in the worship in the Temple. The royal family had to have sound judgement to rule a nation. 

When it comes to Joseph and his wife it was especially delicate because both aspects, the priestly and the royal, were involved. Joseph was of the royal line of David, as Matthew chapter one shows. His wife was of the priestly line of Aaron as Luke chapter 1 verse 36 and verse 5 show. She was a cousin of Elizabeth who was defined as a daughter of Aaron.

So how old were they when the parents decided they were a fitting couple for the future? That could be any age before adolescence. Their ages may have been similar but usually the male is older. According to Hebrew custom and law, parents would then make a formal agreement that a young girl was promised to a young boy. They were then excluded from making any further arrangement for their children. 

Once grown up the children have the right to decide whether to go through with this arrangement. The age of manhood for a boy, that the the age he was able to make this decision, was a minimum of thirteen years old. That does not mean they married immediately but that the deal had been set. The girl, still usually premenstrual, had also to give her consent.  

The ceremony is called betrothal in many Bibles. In Hebrew custom it is called sanctification, kiddushin. The boy and girl are sanctified, set apart, for marriage. This betrothal was solemnised by a gift like a ring signifying the ‘purchase’ of the bride. She agrees by accepting and the young man becomes her husband at that moment. This ceremony celebrated between the families is called erushin. 

This is equivalent to marriage in the modern, western world. Both the couple and the families have given their solemn agreement. It is a public ceremony and the communities are there to witness.
But this is not all. The bridegroom is still young, as is the bride. They do not have independent means. So the bride can stay with her parents while the bridegroom prepares a home for his wife. They have started on a life of total commitment to each other.

So now we come to the Home-coming. When the husband feels that all his ready for his wife, he sends a party out to the parents' house to say they may all come and he is ready to receive them. That is described in the NT. 

Once he brings the wife over the threshold of his new home they have arrived at another stage in life. That is the nisu'in. This is a celebration and should not be considered a legal requirement or condition. The bridegroom welcomes the bride to the new home and usually the whole community is in festive mood. The parable of the ten virgins, Mt 25, who wait for the bridegroom shows that the nisu'in was still part of first century custom. And it is important in the whole theology of the Bible, about God's relationship to his people as a wedding and marriage. 

What if the building of a house by the husband is not necessary? Then the couple are still considered married. They are free to have children but the bride must leave the shelter of her parents. To show that this erushin or 'betrothal' of the KJV is fully marriage, Jews in the first century and Jews today need a divorce, called a get, if they break up. Betrothal is not the equivalent of modern engagement.
  

Let us return to the original question: how old were Joseph and his wife when they had Jesus?
The birth of Jesus to Mary or Mariam (her name in Greek NT) was miraculous. Not because she was young. But because she was old! The NT scriptures say the couple were betrothed. That is they were fully married. If she were young and she became pregnant it would hardly be a miracle.

Birth miracle

So what was behind the miracle? The first thing to notice is that the NT does not say that they were young. It says the opposite. They were very old!

Luke starts by describing the miraculous birth of John the Baptist to his aged parents, Zacharias and Elizabeth. He also describes Anna the prophetess in her old age and her marriage. 

Luke 1:38 says that both Mariam and her cousin Elizabeth (Elisheva in Hebrew), mother of John the Baptist, became pregnant when in ‘old age’ (Greek 'in their gera' — the term used in geriatrics). Both had been married for many decades — they were old and the ‘betrothed’ of the KJV means ‘married’ in Jewish/ Hebrew law and custom. Cousins are usually around the same age.

Miracles of conception to women in their advanced years show God’s power and the direction of his plan for mankind: Sarah, Abraham’s wife, Rebecca Isaac’s, Rachel mother of Joseph, Hannah, mother of Samuel the Prophet, who anointed David. Mariam, the sister of Moses and Aaron, also had children in her old age. Sarah was in her menopause and convinced she could not have children and said so to God’s messenger!

Given that Mariam, Joseph’s wife was advanced in years, Joseph too would be old, or most probably older, at the time of the birth. Then they not only had Jesus but probably 7 children as well, many named in the NT and secular sources, like Josephus and Eusebius, Hegesippus.

That is the miracle. It was one everyone could see.

If this contradicts with modern beliefs that Mary (BVM) was 14 years old or so, and that she was impregnated by a person called the Holy Ghost, that is because in many pagan traditions had gods descending and impregnating young virgin girls. But that is not what the Bible and secular sources of the first centuries say. Becoming pregnant at such an early age was not part of Hebrew tradition. It is part of pagan Greek and Roman culture.

In Hebrew custom, the couple may have become betrothed at that age but they did not live together immediately. The Bible, Jewish tradition and secular sources such as Josephus say that another process had to take place.

Rule out Hollywood

In Hebrew culture, marriage is not like some Hollywood concept of romantic love of incompatible persons. Young children were promised to each other and got to know each other for years before they were married. The purpose of marriage was quite different from the self-centered Hollywood idea. 

It was a covenant-based custom based on centuries-old relationship between God and Israel.

It is a means to have children and show the fulfilment of God's promises to Israel. So a bride had to show she was healthy and fit to have children before copulation took place.

This involved showing that she had regular periods. This was recorded because after each period she had to wash ceremonially in a bath called a mikvah.  These periods had to be regular. The Esseans (or Essenes) of the first century said that the wife had to have at least three regular periods before she was considered fit for even joining her husband in his home. 

In practice that meant that the wife had to show she was mature and healthy. Thus it was likely that childbirth did not take place before the wife was around 17 or in her late teens. 

Old Age

It is speculative to say that because Joseph was not mentioned later he died. His life was also threatened by the high priestly and Roman authorities. He was not only the son of David and the heir to the throne of Israel but also had priestly (Aaronic) blood and could serve in the Temple.

Early sources like Eusebius record that some of his family were long-lived. For example Jesus’s cousin Simon who followed James the brother of Jesus, as Bishop or Superintendent of the ekklesia or Legislative Assembly in Jerusalem, lived more than 100 years old and was then martyred for his firm, unbending belief in Christ. Essenes were also known for their longevity.

Simon was martyred at 120 years old. He was just one of a long series of leaders of the ekklesia so it was probable he died early in the 70s. His birth would have been around 50 BCE. But remember he was the nephew of Joseph. Joseph was the elder son. Simon was the cousin of Jesus, but Simon was much older because Joseph was very late having Jesus as a child.  Joseph, Simon's uncle would have been born a generation earlier. 

So both Joseph and Mariam might have been 70 years or older when Jesus was born.

The family of Joseph and Mariam

For Simon to be the Sagan or Superintendent would mean that he had been trained for that highly complex post. At the time the Sagan was in charge of the Temple and had to be familiar with all the rites and know all the duties of all the thousands of priests there. But Joseph was first in line and after him his son. But apparently as we have discovered, Joseph did not have a son until his old age. 

Simon was not the youngest son of his father, Alpheus or Cleopas. Joseph would have been born several years before Cleopas. Simon would have been born some years after the marriage of Cleopas to his wife Mary. 

So Joseph might have been born around 70 BCE. That would make sense. His wife Mariam would also be about the same age. They would both be around 70 years, maybe older. Abraham was approaching 100 when he and Sarah had Isaac. Both Mariam and Sarah would be considered to be in her 'old age' that is completely unable to have children because she had passed her menopause.  

Meaning of 'Virgin'
The other significant factor would be that in Jewish custom an old woman would also be considered to be a virgin! In Hebrew the main significance of the term 'virgin' is either pre-menstrual or post-menstrual. It does not signify, as the Greek term in the NT, intactness.  

The term 'virgin' revolves around the laws of the Torah which specifies what happens when a woman has a period. That way of thinking is far from the Greek one. It is also far from the modern ideas that some commentators wrongly apply when expounding on the Gospels. First rule is to put the text in its historical and traditional context. 

The laws of Niddah are set out in Lev 19:15 and throughout the Bible.

So when a woman is described as a 'virgin' it can mean one of three things. 

• She is young and has not had a period. 
• She is old and no longer has periods. 
• She has a physical deficiency and has never had a period.

So both Joseph and Mariam would have been in their seventies at the time of the birth of Jesus.

How long would it have been after the marriage of Joseph and Mariam that it was obvious they were not going to have children right away? Five years? Ten years? Twenty years? 

If Joseph had married at just before or around 20 years of age, it would not have been obvious that Mariam was not able to have children for some time. Then it became many decades. That infertility and miraculous birth parallels the births of Isaac, of Jacob, of Samuel and others whose fervent prayers were not only fruitful but a sign to all the world. 

These issues are dealt with in detail in the book, “Jesus, James, Joseph and the past and future Temple” (available also as a free eBook zt academia.edu/43233588).

Why was Mariam shocked to learn she would bear Jesus?

In the Gospel of Luke a virgin betrothed to Joseph was visited by the angel or messenger Gabriel. He announced that she would bear a son to be named Jesus. 

She was shocked. She said in Luke 1:35 'How shall this be, seeing I know not a man?' 

But she was 'betrothed' to Joseph! The verb 'know' must mean have sexual relations with him. 

Isn't that peculiar? Did it need an angel to tell her that marriage leads to children?

The reply of Gabriel is also unusual. It is not what we would expect.

'The holy spirit will come upon you and the power of the Highest shall overshadow you. Therefore the holy born one shall be called the son of God. And behold, your cousin Elizabeth. She also conceived a son in her old age. And this is the sixth month with her that was called barren. For with God, nothing is impossible.' 
Does this expression 'the holy spirit will come upon you' have anything to do with insemination of seed so Joseph was sidelined and rendered redundant? Hardly. A few verses later we learn in 2:25 that the holy spirit 'was upon' someone else. Who? Simeon the retired high priest! He was old and hardly pregnant! 

Was Mary 14 years old?
If as many churches say, Mary -- or Mariam as it is in the Greek NT -- was 14 years of age, why is she so surprised that one day in her marriage she will become pregnant. And what was Joseph doing marrying a 14 year old? Isn't that child abuse? Nothing in scripture supports a teenage girl. The only source of this is pagan mythologies where unmarried, unbetrothed virgins are inseminated by Jupiter or some other god. 
Why does the angel mention an old, grey or white haired cousin called Elizabeth? The word for old age here is the Greek, gera, from which we derive our term geriatrics. Cousins are usually in the same age bracket. This is confirmed in the Greek text. Note the word 'also'.

The Greek says:
And behold, (idou -- Just take a look at that!) your cousin Elizabeth! She also conceived a son in her old age. And this is the sixth month with her that was called barren. For with God, nothing is impossible.' (Or more correctly 'Also she conceived in her old age.' 

Luke also uses the word idou in chapter 2: 25 meaning Surprise, surprise! when Joseph and Mariam meet Simeon the former high priest in the Temple. He was forcibly retired by the paranoid and murderous Herod the Great. He is Mariam's relative. 
For reasons of self-preservation in those dangerous Herodian times they lived quite separately without contact.

'Behold Elizabeth! Also she conceived in her old age.' The 'also' of Luke 1 verse 35 must refer to a miracle relating to either pregnancy or old age ... or both. If Mariam was a young girl or even in her twenties it would not be a miracle that she would become pregnant as announced. A married Jewish woman would expect to have children as part of the reasons for marriage. In her case much more so as Joseph was inheritor of the house of David and her son would be a royal born at a prophetic time according to Daniel when many expected the Messiah. It had obviously not happened, much to her disappointment. Mariam was not some unknown woman but esteemed in her own right as a direct descendant of Aaron, with an authentic genealogy.

If she were in her 20s she should still expect to have children.

Let's make the first correction. Instead 'man' she is asking: 

'How can this be since I have not known (had relations) with my husband?' 

The Greek word here 'andra' does not mean 'man' in the sense of 'any man'. 'I have not been with a man.' That's what the RCC-Protestants say. They say she was a young girl engaged to Joseph but didn't know a man. Was she looking for other men? The text says in KJV she was 'betrothed'! Would she say to the angel that she was looking for someone else to have sex with? That's a crazy and blasphemous idea. 
Engagement

Non-Jewish sectarians are patently wrong because they fail to understand -- or do not want to understand -- what were Jewish marriages/ weddings customs. The answer is simple. They could crack open a Jewish encyclopedia or ask a local Jew at the synagogue. That is not too difficult. Instead they transpose Roman or even loose, modern ideas about 'engagement'. Not so.

Mariam was a daughter of Aaron -- a highly esteemed priestly family with only a few survivors. She was married to a royal son of the House of David. This took place according to ancient custom. Even common people of Israel in first century Judea and elsewhere around the world, followed these customs, according to Josephus and Philo. They kept registers in all the global depositories showing these customs of betrothal, wedding, birth were respected, with names of witnesses. Jews do this today. If a child of a man named Cohen = priest in Hebrew) does not conform to Hebrew rules of marriage, then all his offspring for ever cannot be considered viable as priests.

This regulation was essential if children were to be considered fit for marriage as priests and the same goes for kings and tribal leaders. Ten generations had to be verified by these interlocking methods where many independent registries confirm ancient families.

Betrothal
The first question to ask is: what did the Hebrew or first century Jews mean by 'betrothal'? Qiddushin or Betrothal in the Hebrew or Jewish sense gave the couple the right to live together with all rights of sexual relationship. If either man or wife wanted to separate, a divorce called a 'get' was needed before a judge.

So the shock reply of Mariam: 'How can this be?!' to a pregnancy has to be explained.

We further learn that she was still a virgin! In Jewish custom the term primarily has to do with menstruation. So when a woman says she is still a virgin it means that she was not menstruating or had not menstruated. Amongst the priestly class, no intercourse could take place until a wife had had three successive, regular monthly periods to show she was in good health. That's in Josephus and other sources of the time. The Talmud tractate Niddah written a few centuries later also says that a woman who was old and undergone the change and ceased to menstruate could also be considered a virgin.

Virgin
So the reason for her shock must be (a) she was 11 or 12 and had not menstruated and was naive and thought she never would, (b) she was married a long time she had not had regular periods, and Joseph had never 'known' her, or (c) she was old and had had her menopause some long while ago. Her infertility was certain to her.

Two other points. Firstly, context. The whole of Luke's first two long chapters is about women in their old age. In chapter one we have her cousin, Elizabeth/ Elisheva who was 'stricken in years'. Then we have Mariam / Miriam. The sister of Moses, Miriam the prophetess, married in her old age, Caleb, according to Jewish tradition. She had a flourishing and important family. Then in chapter two we have Anna or Hanna in Hebrew the prophetess of the tribe of Asher. Hanna as a name recalls that of the mother of Samuel the prophet who gave birth in old age, miraculously after much prayer. The NT Anna or Hanna was either 84 years old or much older depending how you read the text. She was 'advanced in years' v 36 having lived with her husband from her virginity seven years. That seems to confirm the Niddah laws of the Hebrew scriptures (and Talmud) are in force.

Secondly we can make a mathematical calculation of Mariam's age. I did this in section 15.17 of the book, Jesus, James, Joseph. It is based on Eusebius. After James the brother of Jesus was killed, Symeon the cousin of Jesus was made the Bishop / Supervisor or Governor/ Sagan of the ekklesia at Jerusalem. He was a younger son of of the younger brother of Joseph called Cleopas or Alpheus. Eusebius gives us his age at his death. We do not know the age of Maria, the wife of Cleopas when she started having children. But the calculation shows that Mariam was old when she had Jesus and later James, Jude, Simeon, Joses and probably three or so daughters.

Mariam was obviously old and past her menopause. That is why she was surprised at the announcement of a birth of a son to come.

Tom Paine debunks the Virgin Birth. What else did he miss?

Is the belief in Mary's Virgin birth is necessary for salvation? The answer to the question is "It depends on what you mean by Virgin Birth".  The conundrum arises because people today seldom read the Bible logically. They confuse what the NT actually says with common custom of "Christmas", nativity and Virgin Birth (that is virginal conception). There are animals and stables, mangers and the story of 'no room for them in the Inn'.
This mythology derives from the non-Jewish and often paganized church of the third and fourth centuries. The dogma of the BVM (Blessed Virgin Mary) is maintained up to the present by Roman Catholics, Protestants and others.
The 18th century best-selling writer and revolutionary,Thomas Paine, opposed this false interpretation. Fine! but he was fighting many shadows and falsehoods. The paganized accretions of the church also added quite a number of falsities that are still present today.
Mary's name was not Mary -- it is Mariam in the Greek NT. This is equivalent to the name of the sister of Moses, a Levite. She was not a young girl but was an old woman like her cousin, Elizabeth. And Elizabeth was equivalent to the Jewish name, Elisheva, Aaron's wife.
Mariam was married and still a virgin according to Hebrew definitions. There is no stable in the NT. There is no inn. There is no cave. The city of David, Bethlehem, was not full of people. It was probably empty except for a few shepherds. (Claiming descent from David was a death sentence in usurper 'King' Herod's regime. No one was even called David in NT times!) No animals, and no stable. But Mariam did not give birth alone. That would have invalidated the genealogy. She needed at least two or three proven honest witnesses.
These false accretions came from Mithraism that was absorbed into Roman religion around the first century. The RC Virgin Birth came from classical pantheism were the gods descended and took human virgins to procreate the demigods.
The Magi did not come at the birth but a year or two later. And there were not three, there were probably hundreds or thousands of Parthian Magi in a caravan that caused the whole of Jerusalem to tremble with fear of another Roman-Parthian war. Parthia had defeated Rome in numerous times in bloody wars and a peace treaty had been made less than 20 years earlier.
And as Paine rightly points out this BVM business adds impossibility to improbability and the illegitimacy of the RC story. In fact it demolishes it. It requires patience and logic to discover and expose lies and falsehoods. A contemporary of Paine was the famous scientist Joseph Priestley. Like many of the scientists of his day, he wrote a huge amount of theology, as in the age of Reason, the logical methodology required was the same. Paine was not up to par on reason. I recommend Priestley's books such as "History of the Corruptions of Christianity" 1782, 'History of early Opinions concerning Jesus Christ'', 'Discourses on Evidences of Revealed Religion' (delivered at the church of the Universalists, Philadelphia 1796 and dedicated to John Adams).
What is important is less the details of history but a willingness to find the truth, for example about the Resurrection and the NT as a whole and act on it.

Tom Paine is considered a hero of American Independence. Born in England, he became an American citizen and then in France during the Revolution was elected to the French Assembly! He wrote a number of books like Common Sense, The Rights of Man, and the Age of Reason, that were best sellers of his time. They still sell well today.
He was raised on the Bible and was able to expose quite a bit of the hypocrisy of the religion of his day. He described himself as a Deist and his rejection of traditional beliefs alienated him from many of his contemporaries.
He was also in conversation with scholars after he wrote this book, so we don't know his final thoughts. He was right to ask questions. But not all of his conclusions are correct. What is useful is the effort to separate the original truth about Christ and the later traditions of men and politicians.
If you consider the so-called Christian traditions of the RC-Protestants as a series of falsehoods overlaid on the biblical account, Paine exposed and removed some of the most pertinent. He said about the Virgin Birth in the Age of Reason that:

Were any girl that is now with child to say, and even if to swear it, that she was gotten with child by a ghost, and an angel told her so, would she be believed?  Certainly she would not.  Why, then, are we to believe the same thing of another girl, whom we never saw, told by nobody knows who, nor when, nor where?  How strange and inconsistent it is, that the same circumstance that would weaken the belief even of a probable story, should be given as a motive for believing this one, that has upon the face of it every token of absolute impossibility and imposture!"

No one would believe her then. No one should believe her today. Yet millions are taught this unbelievable and unprovable claim by a teenager as the foundation for religious belief and obedience to a denomination. Some blasphemously call this girl 'the mother of god.' That is a pagan title of the pagan Queen of Heaven.
Where did the Virgin Birth come from? Why is it held so firmly? The overlay here is ancient and pagan. It is that of the long-held, Greco-Roman gods impregnating human virgins. 
How did paganism get mixed up with Christianity? Thank the fourth century imperial church of Emperor Constantine for this mish-mash! Paine is right to show that such assertions don't make sense. They render the improbable impossible. He exposes it as an imposture. He was a free man and spoke his mind. In the Middle Ages the imperial church would have required his life. In fact Paine almost lost his life for his frankness.
The fraudulent doctrine comes by combining (syncretizing) current beliefs to make a new imperial religion acceptable to all. The imperial church and the popes gave 'Christian' names to the pagan gods. But this allegation of an unmarried teenager claiming a Virgin conception by a pagan-style god is at odds with the Bible.
The NT says the opposite. Jesus had a human father. Mariam says to Jesus about Joseph: 'Your father and I have been searching for you.' The disciples say that Jesus is the son of Joseph. Did the popes know better than the real mother and father?
But wasn't Jesus also divine? Where Paine does not analyze it is in the matter of a second birth mentioned to Nikodemus in John 3. This begettal occurred at the baptism of Jesus as an adult human. It was physically seen as 'the form of a dove'.
A further overlay of lies or ignorance that Paine does not speak of is the confusion of Mariam's marital state. Non-Jews of the RCC etc applied the Roman or  even modern concept of what 'betrothal ' is to the NT. Among Hebrews it was different. It is not Engagement. In Hebrew and biblical custom betrothal=Qiddushin= consecration. It means marriage vows and a divorce is needed to break it. So Mariam was married and with child.
It was clearly a miracle to everyone because she was an old woman! She was pregnant at what was definitely a post-menopausal age. 'By (the) holy spirit' means by the grace of God as elsewhere in NT.
Luke 1:36 says both Mariam and her cousin conceived in their old age (gera as in geriatrics) and as Sarah, Rebekah, Hannah and other holy women. Isaiah 7:7 speaks of 65 years but it is not clear whether this also refers to a married virgin.
No text speaks of a 14-year old. The 14-year old 'Mary' comes again from paganized demigod theology. The Romans assumed anyone older than 14 would not be a virgin.
There is a further overlay of ignorance or lies relating to what modern churches take a 'virgin' to be and what virgin meant to the Jews and in the Bible etc. The first century Jewish Christians were called Nazarenes Acts 24:5 and continued into later centuries. They were clear on these matters. Gentiles were confused.  Paine did not explore the sources of these errors although some of the scientist-theologians like Newton, Whiston, Priestley, Boyle did.
The scientific method requires that each step is proven before one moves to deducing a conclusion. That's why Paine needs to be read, checking and verifying with the Bible, other authors and Jewish writings. Some of this is summarized in chapter 15 of the free eBook
https://www.academia.edu/25051668/Jesus_James_Joseph_and_the_past_and_future_Temple_Version_N36