I Know Not Man
A garden enclosed is my sister, my spouse;
a spring dried up, a fountain sealed.
Song of Solomon 4, 12
Behold thou shalt conceive in thy womb, and shalt bring forth a
son; and thou shalt call his
name Jesus. He shall be great, and shall be called the Son of the Highest; and the Lord
God shall give unto him the throne of David his father; and he shall reign in the house of
Jacob for ever. And of his kingdom there shall be no end. And Mary said to the angel:
How shall this be done, because I know not man? And the angel answering, said to her:
The Holy Ghost shall come upon thee, and the power of the Most High shall overshadow
thee. And, therefore, also the Holy which shall be born of thee shall be called the Son of
Luke 1, 31-35
And Mary said to the angel: How shall this be done,
because I know not man?
Luke 1, 34
If a fortune teller should happen to tell us that we will die of lung cancer from smoking at some indefinite future time, we might ask how this could be possible, since we don’t smoke. We may add that we never smoke, are not smoking now, and have no intention of ever smoking. We could ask the question in these words: “How shall this be, since I don’t smoke?” and add, “How could I possibly die of lung cancer? Is it because I am going to start smoking (be a smoker) after all?” Mariologist Father Rene Laurentine, in his exegesis of Luke 1:34, notes “we must recognize the present tense ‘I do not know’ as having to do with a condition rather than an instant of time. For example, if someone to whom a cigarette is offered replies, 'I do not smoke,' he is understood to mean I never smoke and I am not smoking now.”
At the Annunciation, the Virgin Mary finds herself in a similar situation when the angel Gabriel announces to her that she “will conceive and bear a son.” She is perplexed no less than we would be because she is a virgin (non-smoker) and intends to be one her entire life. Not unlike a non-smoker who is concerned with what is contained inside the crystal ball, Mary anxiously asks the one who is foretelling her future: “How shall this be, since I do not know a man?” And since she has no intention of having sexual relations with any man she might marry, she desires to know how it is that she will have a son. Mary must wonder whether she and her betrothed will have conjugal relations after all. In reply, the angel dispels her confusion by telling Mary that the conception and birth of the child will be supernatural; she will be overshadowed by the power of the Highest and, therefore, her Son will be of holy Divine origin (Lk 1:35).
The original Greek text reads andra ou ginosko (ἄνδρα οὐ γινώσκω) which literally is “man not I know” or in English “I know not man.” The Greek verb ginosko (Present Indicative Active) is in the continuous present which shows a permanent disposition to not know man.  The original Greek translates what Mary says to the angel in her native tongue of Hebrew-Aramaic: ki enneni yodaat ish. The Greek present tense used for Mary’s words in Luke 1:34 corresponds to the Hebrew Aramaic active participle (yodaat) indicating a permanent condition. 
So, Mary has a permanent disposition to not know man, just as the man who says, “I don’t smoke” has a permanent disposition not to smoke. The verb “to know” in the Scriptures is often used as a Jewish idiom for sexual relations between a man and a woman. Idiomatically, Mary is telling the angel: “I don’t have sexual relations with a man.” Now, this Jewish idiom for sexual relations is subject to the same rules of grammar as any other verb is. The verb “to know” may be conjugated in the past tense. We read in Genesis 4:1 in the Septuagint: ‘And Adam knew (αὐτοῦ) his wife who conceived and brought forth Cain.’ In other words, Adam had sexual relations with Eve who, as a result, conceived and brought forth Cain. Eve conceived Cain because she had sexual intercourse with Adam.
But Mary does not have sexual relations with men, so she wonders how she will conceive Jesus. She tells the angel: “I do not have sexual relations with a man.” She never has had sexual relations, and she is not having sexual relations now. Mary is no different from the non-smoker. She has a permanent disposition not to have sexual relations with a man, just as the non-smoker has a permanent disposition not to smoke. It is Mary’s permanent disposition and will not to have sexual relations with any man, which explains why she asks the angel how or by what manner she could ever possibly conceive and bear the Messiah, seeing she has no sexual relations with a man.
The King James Bible translation is accurate in that the verb “to know” is in the Present Indicative Active, but it is misleading with the insertion of the indefinite article “a” before “man”, which we don’t have in Jerome’s Latin Vulgate. The inclusion of this grammatical exponent can create a misunderstanding of God’s written word. The object in Mary’s statement is andra (ἄνδρα) which means “man”, or more precisely the genre of the male sex.  What it does not signify is an individual or specific male, who in this case would be Joseph.
The KJB discrepancy may expand to modern readings like this one: “I do not have a husband.” However, we read in Luke 1:27 that Mary was betrothed (espoused) to Joseph at the appointed time. The couple was already legally married, having observed the first part of the marriage ceremony (Kiddushin) which included the signing of a legal marriage contract. They were, in fact, husband and wife at the time of the Annunciation, which explains why Joseph could divorce Mary as soon as he discovered she was with child (Mt 1:18-19). Andra can mean “husband” in a general sense (Jn. 4:17), but Mary does not say: “I have no husband,” since she already has one whose name is Joseph. The object noun andra does not refer to individual men. There is another word for them which is anthropos (ἄνθρωπός) as in Matthew 8:9. 
St. Augustine explains how it is that Mary should even contemplate asking such a question, seeing that she was betrothed to Joseph at the time the angel appeared to her and obligated to bear children within her religious culture.
virginity also itself was on this account more pleasing and accepted, in that
was not that Christ being conceived in her rescued it beforehand from a husband
who would violate it, Himself to preserve it; but, before He was conceived, chose
it, already dedicated to God, as that from which to be born. This is shown by the
words which Mary spake in answer to the Angel announcing to her conception;
‘How, saith she, shall this be, seeing I know not a man?’ which she assuredly would
not say, unless she had before vowed herself unto God as a virgin.”
Of Holy Virginity
vow and any binding oath to afflict herself, her husband may establish, or her
husband may make void. But if her husband says nothing to her from day to day,
then he establishes all her vows, or all her pledges, that are upon her; he has
established them, because he said nothing to her on the day that he heard of them.
But if he makes them null and void after he has heard of them, then he shall bear
The vow of a woman to “afflict herself” included abstaining from having sexual relations with her husband and having a family so that she could dedicate her life exclusively to God. Under the Mosaic Law, provisions were specifically made for such vows, although normally discouraged. A vow made by a woman like this one, however rare and frowned upon, was permissible since the command to propagate did not apply to females. It applied only to men, which explains why there is no similar statute about vows taken by married men. If Joseph agreed to a chaste marriage, which appears most likely, it was only because he honored the vow Mary had made before they met when she was still a young girl serving in the temple, and by the time the first part of the marriage ceremony (Kiddushin) was observed when a contract would have been drawn up and signed making Mary his legal wife.
Thus, Mary basically asks how it is possible she can conceive and bear Jesus, seeing she is a virgin who intends to have a chaste marriage. She wouldn’t have asked how if she intended to fully consummate her marriage with Joseph after he brought her into his home upon the second marriage ceremony or Nisuin (Mt. 1:20, 25). And in reply to her question, the angel explains how it is she will retain her virginity and keep her vow to God despite having a child: by the power of the Holy Spirit.
In a grammatical nutshell, Mary asserts she does not have sexual relations with a man within a time frame that includes the future simple. Luke has Mary speak in the present tense, active voice, and indicative mood; since the angel does not say that she has conceived or will conceive at some specific time. The fact is she does not have sexual relations with any man, who includes her husband. Her not having sexual relations with men characterizes what she is, viz. a virgin. The verb tense signifies an ongoing state (of not having sexual relations with a man), not an instant of time, that extends beyond the present moment and embraces the future. Mary asserts she does not have sexual relations with a man – not now or ever – despite the angel’s announcement.
Indicated by the present active voice, Mary’s condition is an objective fact that Mary asserts continues beyond the present moment and into the future, including when she is supposed to have a son. The angel’s announcement that she will conceive and bear a son conflicts with her unchanging, ongoing state. This explains her perplexity. The conjunction “since” serves as a logical connector.  The Greek exponent epei (ἐπεί) in this case can be paraphrased as “because”: Because Mary does not have sexual relations with a man, including her husband, she wonders how she will conceive and bear a son. We mustn’t presume this adolescent of marriageable age knew nothing of biological human reproduction.
The indicative mood of the verb ‘to know’ tells us Mary has no intention of having conjugal relations with her husband Joseph regardless of what the angel says. For this reason, she can’t possibly be the mother of the expected Messiah, unless God has other plans for her which she is presently unaware of. The angel Gabriel reveals the Divine intention to Mary in the following verses. Only then does she pronounce her Fiat without further ado and the angel depart (Lk 1:38).
Then he brought me back to the outer gate of the sanctuary,
which faces east;
and it was shut. And he said to me, “This gate shall remain shut; it shall not be
opened, and no one shall enter by it; for the Lord, the God of Israel, has entered
by it; therefore, it shall remain shut.”
Ezekiel 44, 1-3
Therefore, we should keep in mind that the verb “to know” in the first person (ginosko) does not have to do with an instant of time, but rather with Mary’s state itself. Mary does not tell the angel: ‘I am not having relations with a man (my husband) now’ or ‘I have not had any relations with a man until now.’ There would be no reason for her to say these things since the angel does not tell her that she has conceived or suggest even remotely that she will conceive the child immediately or before her marriage is formally solemnized upon the second and final wedding ceremony (Nisuin). The original Greek text reads: “I do not know man.” Mary has sexual relations with no man ever – not presently, not ever. And since the verb is in the active indicative mood, there is an emphasis on the progress of the negative action (do not know a man) which continues when she is supposed to have the child – whenever that will be.
The Greek present tense denotes either a progressive or repetitive action. In this case, it is progressive and indicates a continuance of state which bears on a future event. So, there is an emphasis on the progress of an action (does not know or have sexual relations with a man) or a state (virginity) which extends into the future and affects it. The verb “to be” (estai / ἔσται) is in the simple future tense.  Mary’s present state in real-time is of no concern.
So, it isn’t really a question of whether she has had relations with her betrothed until now or is having relations with him when she shouldn’t be. The question is whether a woman who does not have sexual relations with a man can ever conceive and bear a son. The angel explains how in the following verse: “The Holy Spirit will come upon you, and the power of the Highest will overshadow you.” There is something about Mary that Luke wishes to give testimony to, that perpetually she is a virgin. If ever there were a conclusive Scriptural proof-text for the Catholic dogma of the Perpetual Virginity of Mary, it would have to be Luke 1:34: “How shall this be done, because I know not man?”
Therefore, the Lord himself shall give you a sign.
Behold, the virgin shall conceive, and bear a son,
and his name shall be called Emmanuel.
Isaiah 7, 14