1. Question Restatement:
“In A Beginning” vs. “In THE beginning”? What is the proper way to interpret Genesis 1:1?
2. Clarification - In Hebrew, the definite noun can be indicated in more than one way:
NASB, Genesis 27:15, Hebrew Interlinear - Then Rebekah took the best garments of Esau her elder son, which were with her in the house | בַּבָּ֑יִת, and put them on Jacob her younger son.
So, the question's observation about the omission of the traditional "H" definite article is not valid.
In fact, this ambiguity was only tackled by the Karaites (900 AD), (or perhaps Rabbinicists? Long story / debate...), by placing a "vowel pointing", (see above), into the text, to indicate a definite noun, one "beginning".
But vowel pointings in 900 AD are not "proof" of how Biblical passages were interpreted 1400+ years earlier, let alone evidence that Biblical authors were even intendeding to be clear, (many Scriptural writers were intentionally vague).
3. Answer - Multiple interpretations can be held simultaneously:
The false dilemma behind this question is the assumption that Genesis must be about: A.) THE beginning or B.) the LAST beginning of a series of beginnings. This wrongfully excludes another possibility:
The author of Genesis might have been alluding to another beginning - still yet to come. Genesis might be "A FIRST" beginning, (rather than "the only", or "the last").
The possibility of Genesis being "a first beginning" is very consistent with "New Earth"-ish theologies in Isaiah, other prophets, and the New Testament.
4. Answer - Holding multiple interpretations is valid and consistent:
Theologians today, (and historically), have had a very difficult time with ambiguity in Hebrew Scripture. But, this is like pointing out English teachers have inconsistent interpretations of Maya Angelou's poetry.
Genesis 1 is clearly poetic, in form - as most Hebrew is. Poetic authors expect the readers to exercise discretion - to explore, to contemplate, and seek out meanings and significance.
In other words,
"In the beginning" and
"In a beginning" and "In the First Beginning", are not mutually exclusive. Here, the reader is invited into a contemplation, that expects them to pursue intimacy with God for the proper solution, (Scripture is full of this kind of expectation - with the aid of the Holy Spirit, through prophets, etc.).
There is no reason to exclude the plausibility of a "Play on Words":
Personally, I feel there is most merit in observing the fact that the very first word in the Bible appears to be an amalgam of multiple words ("beginning" and "create"), which doesn't exist in any other text, and that no editor, (Ezra, Documentary Hypothesis, etc.,), understood it as appropriate and significant, (the vowel pointing "correction" only happened in 900 AD).
In a Documentary Voice:
In The Beginning, God created ...
In a Narrative Voice:
[While / When / In] Creating, God created the Heavens and the Earth.
In a Prophetic Voice: Bereshit as a compound of both "Head/Beginning" and "Create" -
During the First Creation, God Created ...
- or perhaps, "A first creation, God Created ..."
There is no theological reason, no hermeneutical reason, to force ONE particular interpretation onto the reader when the writing style is poetic. This idea is completely contrary to poetic and metaphorical writing.
Another non-literal phrase in Genesis 1:
If the Sun wasn't set as a "sign" for days until the fourth day, then how were the first three, literal, 24 hour periods reckoned if the Sun wasn't present to serve this purpose? This requires any reasonable reader to infer that the text isn't speaking of literal "24 hour" days.
It is a very bad argument - to dogmatically state - that poetic language can, and should, only be interpreted one way.
Poetic interpretation often clashes with "grammatical exegesis" - and, that is actually okay.
Conclusion: The fact that this verse can be interpreted in so many non-contradictory ways points to its significance. On the other hand, constricting this verse to only one interpretation removes significance and its presence in the text is rendered meaningless. A restrictive interpretation requires the reader to contemplate "the beginning of the universe" - an idea not in any Biblical context. However, poetic interpretations require the reader to make inferences about the ages of mankind - an idea which appears throughout Scripture.