Mr. Wilson provides some rebuttal with respect to typical arguments against the theory of Mary's perpetual virginity (arguments presented by his opponent, Mr. Schroeder), which I will address in turn.
(1) Opponent's argument "Matthew 1:18’s “before they [Joseph and Mary] came together,” is evidence of Mary and Joseph’s eventual consummation."
(a) Mr. Wilson's rebuttal:
In fact, all the tense of this phrase means is that after they were betrothed, but before they were allowed to be sexually active, Mary was found to be pregnant. Recognizing this, the Jerusalem Bible translates the passage in the following way: ”His mother Mary was betrothed to Joseph, but before they came to live together she was found to be with child…” Check a commentary.
(b) I respond:
Matthew 1:18 Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
The primary issue here is whether the word for "come together" (συνέρχομαι) refers to sexual union. Here we need to be cautious. The word does encompass a range of meanings, some of which are clearly not sexual union but rather the assembling of a mob or the like. The context, however, in this case is determinative, for we are not speaking of a crowd but of an espoused (betrothed) couple.
Parallel usage in Scripture does indicate that this term is a euphemism for the sexual act:
1 Corinthians 7:5 Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
There is, however, also a secondary issue. Strictly as a matter of grammar and logic, the fact that the verse says "before they came together," may not imply that they eventually came together. Instead, it could point simply to the expected course. (More on this, below.)
(2) Opponent's argument "Matthew 1:24’s “Joseph knew her not until” foreshadows a time whe Joseph will “know” Mary."
(a) Mr. Wilson's response:
-In fact, any good commentary will tell you that all that what is being said here is that Joseph and Mary did not engage in sexual intercourse during the period which preceded the birth of Jesus. Nothing is said about after, simply during. To quote the Eerdmans Biblical Commentary (not a Catholic source) we read that “it neither affirmed nor denied that she remained a virgin for her life.” Matthew has no interest in Mary’s perpetual virginity, and he is not commenting on it here. You can also consult Bloomberg or Gundry (Protestant commentators) if you like, both of whom agree.
To quote Jerusalem again: “He [Joseph] took his wife home and, though he had not had intercourse with her, she gave birth to a son…”
(b) I respond:
24Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife: 25And knew her not till she had brought forth her firstborn son: and he called his name JESUS.
The Jerusalem Bible's translation is obfuscatory. The above literal translation is much better. That's not the primary point, however.
The primary point is that our (Reformed and even most other Protestants') rule of faith is not commentators but Scripture. Thus, Eerdmans' has spoken and the case is closed, is not our watchword.
A secondary point is that the phrase "knew her not until," as a matter of strict logic conveys only information about what happened before Jesus' birth. Thus, some commentators have felt justified in the kind of comments that Mr. Wilson has identified.
On the other hand, the words are not part of a syllogism in a logic textbook. They are part of a sentence in which it is mentioned that Joseph "took unto him his wife," referring to Mary. In such a sentence, the most natural reading of the text is to view it as explaining the extent of Joseph's deviation from ordinary marital relations, particularly in view of the larger context, and the comment in verse 18 (already discussed above) regarding the expectation (at a minimum) of future sexual union.
(3) Opponent's argument "Matthew 1:25’s statement that Mary brought forth her firstborn suggests that later children were to follow."
(a) Mr. Wilson's response:
-Not so. Consider the following: Fitzmyer speaks of an ancient funerary, dated 5 B.C. recalling the death of a Jewish woman. It reads: ‘In the pangs of giving birth to a firstborn child, Fate brought me to the end of my life.’
Protestant commentators (Morris, Green, Nolland) all with their knowledge of the Biblical languages (do you envy them Mr. Schroeder?) confirm that the passage makes no statement about later children.
(b) I respond:
I think Mr. Wilson's comment here is essentially correct. That is to say, "firstborn" (πρωτοτόκος) doesn't in itself indicate that Mary had other children. Furthermore, the emphasis in the text is on Mary's virginity prior to Christ's birth, and consequently "firstborn" serves to emphasize that there were no children of Mary's before Jesus, rather than to emphasize the existence Jesus' brethren.
On the other hand, given our knowledge that Jesus had brethren, we may view the use of the term "firstborn" to emphasize that from among the sons of Mary, Jesus was the first (since those living at the time might have recalled the fact that Jesus was not an only child). In other words, while "firstborn" is not compelling evidence against perpetual virginity, it fits slightly better into the non-perpetual-virginity theory than the perpetual-virginity thoery.
(4) Other arguments
Mr. Wilson does not address the other arguments that are normally presented against the assertions of Mary's perpetual virginity, such as the arguments related to the fact that Jesus had "brethren" and the suspicious point of entry of legends of perpetual virginity into "tradition."
Ultimately, however, the matter reduces to this: Scripture is more easily reconciled with the non-perpetual theory than with the perpetual theory. The non-perpetual theory is not only harmonious with a natural reading of Matthew 1 and with the accounts of Jesus' brethren, but also with Paul's teaching regarding proper marital relations. In contrast, the perpetual virginity hypothesis has no reasonable exegetical Scriptural basis, and very limited and suspicious traditional basis in the early church era.
I'm not sure if Mr. Wilson plans to provide a part II, but if so, I will be looking forward to it.