The Orthodox Church titles him "Joseph the Betrothed." My understanding is that the intention was to remain in the betrothed state, which, as I understand, included "legal" co-habitation, but not licit "knowing." My understanding is that they never intended to marry, since it is not really a legal marriage unless there is "knowing."
When she became pregnant, Joseph assumed that it was by "a secret union" with another man (as our liturgical texts say). It is understandable that he would not want to marry her, since she had obviously, in his eyes, broken the vow that was the reason for the betrothal in the first place -- the preservation of her virginity.
If he loved her and wanted her as his wife in the ordinary sense that Protestants believe, his first reaction very well might have been to do the "best" thing, and take her to wife and decide to forgive and forget, covering her sin. If he had wanted her as his wife, but no longer wanted her because he was betrayed and shamed, his initial reaction might very well have been, in his anger, to do the "lawful" thing.
His actions in putting her away quietly reflect the actions of a distant relative who loves her enough not to want her to be stoned, but who no longer sees a reason to continue with the betrothal. This all fits in very well with Orthodox Tradition -- better, in my opinion, than does the Protestant explanation, although it is also a valid explanation.
He was instructed by the angel to take her to wife (i.e. "make an honest woman out of her" in the eyes of the world.) Our tradition is also that this formal taking of her to wife was to deceive Satan. In any event, they could not continue in the state of betrothal. The whole reason for Matthew 1:25 is to make clear that with the change from betrothal to formal, outward marriage, there was still no physical union -- making no mistake about her virginal conception. Consider that even though the Bible says that he took her to wife, this was only for the benefit of appearances to the world, since she obviously wasn't really his wife at that time, since they didn't consummate the marriage.
Aha. I was remembering hearing the same thing somewhere, and my guess was Fr. Pacwa of EWTN. However, I could not ascertain that yesterday. Do you have a source for this belief? See my 6678 and the antecedent discussion.
In my earlier digging around on both Catholic and Protestant sites, one thing I thought was in common was that in betrothal, the "bride" and "groom" did not live together during the betrothal. The tell tale sign that the marriage had actually taken place was that the woman came to live with the man. Here is an excerpt from the writings of Pope John Paul II EWTN Library :
"In presenting Mary as a "virgin", the Gospel of Luke adds that she was "betrothed to a man whose name was Joseph, of the house of David" 1:27). These two pieces of information at first sight seem contradictory.
It should be noted that the Greek word used in this passage does not indicate the situation of a woman who has contracted marriage and therefore lives in the marital state, but that of betrothal. Unlike what occurs in modem cultures, however, the ancient Jewish custom of betrothal provided for a contract and normally had definitive value: it actually introduced the betrothed to the marital state, even if the marriage was brought to full completion only when the young man took the girl to his home."
My version on this says:
Matt. 1:20 : But after he had considered this, an angel of the Lord appeared to him in a dream and said, "Joseph son of David, do not be afraid to take Mary home as your wife, because what is conceived in her is from the Holy Spirit.
Is the phrase you use in the post "take her to wife" intentional, to address this issue?