Having used the expression “ancient Jewish monotheism” in the sub-title of my 1988 book (One God, One Lord: Early Christian Devotion and Ancient Jewish Monotheism), it’s been interesting thereafter to note the apparently rising interest in “monotheism” in ancient religion. E.g., there is now a programme unit on the topic in the Society of Biblical Literature annual meeting, and Nathan MacDonald directs a major, funded research project on the topic: http://www.uni-goettingen.de/en/122432.html
On the other hand, a number of scholars have rightly noted the problem in using the term “monotheism” for any of the traditional religious traditions to which it has often been applied. Per most dictionaries, “monotheism” means denying the existence of any but one deity. But it is not clear that ancient Jews and Christians denied the absolute existence of other gods, and in at least some texts it seems clear that they did acknowledge that other gods exist. So “monotheism” as typically defined is dubiously applied to these traditions.
Since my 1988 book, I’ve urged that if “monotheism” is used at all it has to be informed by the specifics of the beliefs and practices of those to whom we apply the term, and I’ve also contended that there are varieties of “monotheism”. So, e.g., I proposed that the chronological data require us to see the eruption of a remarkable Jesus-devotion originating as a religious innovation within Roman-era Jewish tradition, producing a novel “mutation” in ancient Jewish monotheism in which two distinguishable figures (God and Jesus) are programmatically treated as unique recipients of devotion.
In two more recent essays (not yet published), I’ve noted that scholars now frequently refer to “pagan monotheism”, typically meaning by that expression ideas of a single “high-god” over a pantheon, or a single divine substance of which all the particular deities are manifestations. So long as we use the full expression “pagan monotheism” and note that it is quite different from ancient Jewish and Christian beliefs and practices, that’s fine. It’s not “monotheism”, it’s “pagan monotheism”.
On this premise, I’ve then also argued that we can use the expression “ancient Jewish monotheism” to designate the well-known exclusivist stance characteristic of second-temple Jewish tradition: the insistence that only the one biblical deity is worthy of worship, and that worship of any other being (including heavenly/divine beings) constitutes idolatry. This isn’t “monotheism” (as Englightenment thinkers imagined it), it’s “ancient Jewish monotheism”.
And in my most recent essay on this matter (presented at a recent mini-conference in Lausanne), I’ve proposed that we use the expression “early Christian monotheism” to designate the distinctive exclusivist stance characteristic of early Christianity. This involved a rejection of the worship of “the gods” in favor of the one biblical deity (as in the parent tradition of second-temple Judaism), but with the distinguishing new element of including the glorified Jesus as also rightful (even required) object of faith and co-recipient of worship. Again, this isn’t “monotheism” of the dictionaries; it’s “early Christian monotheism”.
Finally, because my use of the term “binitarian” to describe earliest Christian devotion has drawn so much misunderstanding, I’ve dropped it in favor of referring to the shape of earliest Christian devotion as a “structured dyad”: God (“the Father”) and Jesus, with Jesus defined and reverenced typically with reference to God (i.e., not as a second deity, but as the unique expression and agent of the one deity). So, we could refer to earliest Christian devotion as “dyadic” in shape. Hopefully, this term will occasion less misunderstanding, and fewer accusations of trying to import later conceptions into the earliest expressions of Jesus-devotion.