http://www.newadvent.org/cathen/02767a.htm
The chief objection against the Catholic position is taken from Matt 1:25: “He [Joseph] knew her not till she brought forth her firstborn son”; and from Luke 2:7: “And she brought forth her firstborn son”. Hence, it is argued, Mary must have born other children. “Firstborn” (prototokos), however, does not necessarily connote that other children were born afterwards. This is evident from Luke 2:23, and Ex 13:2-12 (cf. Greek text) to which Luke refers. “Opening the womb” is there given as the equivalent of “firstborn” (prototokos). An only child was thus no less “firstborn” than the first of many. Neither do the words “he knew her not till she brought forth” imply, as St. Jerome proves conclusively against Helvidius from parallel examples, that he knew her afterwards. The meaning of both expressions becomes clear, if they are considered in connexion with the virginal birth related by the two Evangelists.
http://www.cathtruth.com/catholicbible/evervirg.htm
1. The conjunction “until” in Scriptural usage expresses what has occurred up to a certain point, and leaves the future aside. Thus God says in the book of Isaias: “I am till you grow old” (Isaias 46:4). Are we to infer that God would then cease to be? Again, God says to His Divine Son: “Sit Thou on My right hand until I make Thy enemies Thy foot-stool” (Psalm 109:1). Will the Messias, once His enemies are subdued, relinquish His place of honor? St. Matthew’s principal aim was to tell his readers that Christ’s birth was miraculous and that Joseph had no part in the conception of Mary’s child. His statement is confined to this point.
In itself the statement, “He knew her not till she brought forth her first-born Son,” neither proves Mary’s subsequent virginity nor contains an argument against it. Speaking as he does, the Evangelist in no wise affirms that the abstention mentioned by him ceased after the expiration of the time indicated.
To say that the exclusion of an event up to a certain point implies that it occurred afterward, is pure cavil. In fact, one would find it difficult to believe that the sacred writer, after insisting so strongly on Mary’s anterior virginity in the opening verses of the chapter, could suddenly imply that it ceased later on. If Joseph abstained from the use of the union preceding the angel’s message, who could think that after Mary had brought forth the Son of God, he should feel less reverence for the temple of the Trinity?
Not sure why you posted all that copied and pasted info to me. My response was to the illogical correlation that Brian Kopp used in response upthread. He actually proved the other poster’s point.
Mary was a virgin TILL she had Jesus....
His aunt voted Republican TILL she died...
If the scripture had said Mary was a virgin until she died, he might have a point.
The simple fact that you must perform such intellectual gymnastics causes a reasonable person to question not only your conclusion, but your motive.
It is like reading the conspiracy theories regarding 9/11.