Reviewing my notes, I can see several ways in which this can be argued to be only plausible, not certain. And I would have to agree with that, at least on the basis of the passage that I cited. The interpretation being offered is plausible but not certain. Yet it may be worth holding in mind for consideration when reading the rest of the text, to see if it can possibly shed light on other interpretations.
(Lightfoot's translation)
5:2 Yea, and we love the prophets also, because they too pointed to the Gospel in their preaching and set their hope on Him and awaited Him; in whom also having faith they were saved in the unity of Jesus Christ, being worthy of all love and admiration as holy men, approved of Jesus Christ and numbered together in the Gospel of our common hope.
6:1 But if any one propound Judaism unto you, hear him not: for it is better to hear Christianity from a man who is circumcised than Judaism from one uncircumcised. But if either the one or the other speak not concerning Jesus Christ, I look on them as tombstones and graves of the dead, whereon are inscribed only the names of men.
This passage supports an observation that this letter is written in opposition to Hellenistic so-called "Judaizers" (note the reference to "Judaism from one uncircumcised"), although I wouldn't use that specific term. The possibilities for such opponents are varied and tantalizing, but unfortunately it isn't really part of the aim of the letter to explain the ideas being propounded by his opponents, which would be interesting to know. What we do learn here is that they "speak not concerning Jesus Christ." Someone might interpret this (beyond what he says) to mean that they do not speak of Jesus Christ correctly. But that's not necessarily true because there is already a lot of known literature where those texts "speak not concerning Jesus Christ," too much to be a coincidence IMO, so we can be morally sure that there were Christian-adjacent ("pre-Christian"?) and/or heterodox Christian persons who did not speak of Jesus. Here is some of that literature, some of which is sometimes categorized as "Jewish" or "pre-Christian" (but which is still relevant towards shedding light on opponents who may "speak not concerning Jesus Christ"). Note that this literature comes from varying perspectives, and some of it is dependent on the Gospels and/or Paul, while other material is not; in at least some cases, it isn't clear whether they
would refer to Jesus.
Odes of Solomon
Philo of Alexandria
Eugnostos the Blessed
Testaments of the 12 Patriarchs
The Shepherd of Hermas
Dialogue of the Savior
Gospel of Mary
Second Apocalypse of James
First Apocalypse of James
On the Eighth and Ninth
more here:
https://peterkirby.com/a-table-of-chris ... itles.html
Uncircumcised proponents of so-called "Judaism" (in the words of Ignatius) may have had Hellenistic Jewish beliefs that were similar enough to be appealing to those that Ignatius addressed to be tempting or confusing for his "Christians," which brings into question the authority of Ignatius and his doctrine. One advantage that these proponents had claimed (and they would be explicit on this, as found later in the letter) is that they were able to found their ideas on the scripture, calling on the antiquity and authority of those writings.
People with these kinds of beliefs could have arisen independently of the influence of (for example) the Pauline letters and the Gospels, both of which refer extensively to Jesus. Meanwhile, Ignatius stood in that stream of religious ideas and indeed uses the very term "Christianity" for it, calling his opponents advocates of a type of "Judaism." These Christian writings don't have the authority of scripture for Ignatius. Such a point of view, where the Septuagint was scripture, was not an unusual position to take for early Christians, especially in the second century (during which a trend to adopting new, Christian scripture was introduced for the first time).
So far I have said that these people "speak not concerning Jesus Christ," their ideas could sound like "Judaism from one uncircumcised," and their ideas could be similar enough to those held by Ignatius to put them in direct competition with him for converts, so probably not just something that is more similar to the religion of Josephus or of the rabbis of the Talmud. Notice in the phrase "either the one [Christianity from a man who is circumcised] or the other [Judaism from one uncircumcised] speak not concerning Jesus Christ," this would make sense if they both could speak of such things in a context where Jesus Christ could potentially be named or not named. With comparison to the literature that I mentioned, such things would regard just this: a second divinity besides God. Some of the opponents of Ignatius (not addressed here) would refer to Jesus, but at this point Ignatius is dealing with those who would not.
At this point, a minimal conception of the opponents of Ignatius here begins to form. They were not for example a hypothetical group interpreting the letters of Paul as referring to an exclusively celestial/sub-lunar Jesus or interpreting a gospel as referring to a purely allegorical Jesus. They were similar at a basic level to known groups who wouldn't refer to Jesus Christ at all but who would explain a theology of a second divine figure, developing it from the Old Testament. It's not possible to pin down exactly which of the mentioned literature is the best analogy in the particulars, but in the general outline that much is clear enough, as much as anything can be here.
What language we should use to describe them is a good question. Based on the literary analogies already mentioned, some of those would be categorized as "non-Christian" Jewish, while others would be categorized as "Christian" even if the author didn't (and perhaps wouldn't) refer to Jesus Christ. Finding where the dividing line should be isn't easy, given ambiguities both in these categories and in the texts themselves (e.g. perhaps some of them would refer to Jesus and happen not to do so). If we're looking at the analogies where the texts don't show the influence of NT texts such as the letters of Paul and the gospels, generally these are usually termed "non-Christian." From a history of religions perspective, some of them are sometimes called "pre-Christian" in anticipation, to the extent that their ideas may have contributed to some parts of what contributed to Christian religion and/or because their ideas are similar in some ways to Christianity but not influenced by it.
So in summary we would have here "pre-Christian" Hellenistic Jews, who are opposed to Ignatius because what they believe they consider to be based more strictly on the Old Testament. Not only is it based on the Old Testament, but given that they don't refer to Jesus, we can say that it is not based on the letters of Paul, on written Christian gospels, on stories about Jesus, or other similar "Christian" sources. These "pre-Christian" Hellenistic Jews are proudly independent of the "Christianity" of Ignatius. Interaction with Christians like Ignatius may make "Christian-adjacent" (or something else) a more appropriate term, given that there would no longer be complete ignorance of Christians.
As noted, this hypothesis (particularly the "Christian-adjacent" / "a second divine figure" part) can thus far be regarded as plausible but not certain. The hypothesis is being introduced here because it might help with understanding the text. I don't intend to get bogged down in arguments about whether this hypothesis can be argued to be demonstrably true, and I don't rely on this hypothesis as more than a plausibility (i.e., I am not saying this hypothesis settles the long, drawn-out debate-like discourse on the passage that is Giuseppe's subject in this thread, and I am not using it that way).
