What could John have known about who Jesus really was? On sound critical grounds, I think we can say a lot more than is typically done. (1) It is undisputed that John the Baptist lived and baptized Jesus (he’s mentioned in Josephus as a righteous man, and all four Gospels connect him to Jesus). (2) Isa 40:3 is used in relation to his ministry in all four Gospels, in which he is viewed as a forerunner to one greater than himself. If John’s Gospel is independent from the synoptics, this makes for a very compelling case that Isa 40:3 goes all the way back to John himself as a self-description. (3) The criterion of embarrassment shows that he really did baptize Jesus (cf. Matt 3) and that he was probably uncomfortable doing it. John’s Gospel, for example, omits the actual baptism, but speaks of John’s humility in relation to Jesus.
What did John definitely know about Jesus? He almost surely knew of the incriminating evidence about Jesus’ birth—that is, that he was conceived out of wedlock (among other reasons, the two men were related; also, John 8:41, 47, implies that it was common knowledge that Jesus’ birth was not proper). Now, if this is the case, then we have to ask: Why would John knowingly promote Jesus? After all, his own disciples left him to follow Jesus. What parallels are there in Judaism that have a forerunner in the first place? And what parallels are there that have a godly forerunner promote someone greater than himself when that forerunner knows that the one he is promoting had dark beginnings? Would this not possibly even disqualify such a person from a great ministry?
Preliminary soundings suggest the following:
OT: Deut 23:3—“Those born of an illicit union shall not be admitted to the assembly of the Lord. Even to the tenth generation, none of their descendants shall be admitted to the assembly of the Lord” (NRSV). As well, sexual immorality and idolatry are used almost interchangeably in the OT (e.g., Hosea), as though they were of one cloth.
DSS:“fornication … belongs to the children of darkness, from whom the children of light must separate themselves as sharply as possible.” —s.v. povrnh,ktl. in TDNT 6.588 (article by Hauck & Schultz). That some suggest that John was trained in the Qumran/Essene community would of course support the idea of John’s negative attitude about the offspring of an illicit relationship (although I seriously question whether John was a part of such a community).
Philo—“Philo allegorizes the concept [of porneiva]. povrnoi stand for polytheists…, who are for him the sons of harlots…” (TDNT 6.588) Philo (1st century BCE) is motivated by apologetic purposes. He is ashamed of the immorality of his own people and thus allegorizes. But that he equates the offspring of prostitutes with idolatrous people may be significant.
If the evidence of Judaism, including Second Temple Judaism, is overwhelmingly that illegitimate offspring were viewed as tainted, ungodly, disqualified to lead the nation, then it seems that the kinds of positive statements that John makes of Jesus are due to something else that has tipped the scales in favor of Jesus. In other words, it may be that John may well have embraced the virgin conception or else he would not have been able to unashamedly promote Jesus as the ‘lamb of God who takes away the sin of the world’ (a statement that even C. H. Dodd finds authentic). All of the above may well become a significant cause to explain the effect of John’s self-consciousness (in which he is utterly self-deprecating) in relation to Jesus.
I’m not saying that John necessarily believed in the virginal conception of Jesus; but the evidence seems to suggest that he was aware of the popular view of Jesus as having been conceived in fornication, and yet he did not accept the social stigma, deeply rooted in the Judaism of the day, that is normally associated with one whose parentage is not pristine. Although it may be saying too much that John embraced the virginal conception, it does not seem to be too much to say that John thought of Jesus’ origins as somehow supernatural.
He, like many others, may have withheld judgment about Jesus’ origins and allowed Jesus’ actions to speak. But that view is problematic: Before Jesus had any public ministry—a ministry which did not begin until John baptized him—John was already seeing himself as lower than Jesus, as the man who needed to be baptized by Jesus rather than vice versa, as one who needed to decrease as Jesus increased. All of this fits with the idea that John held to some sort of supernatural origin for Jesus. The criterion of coherence thus fits perfectly well with the picture we see in the Gospels; any other view distorts what we know about John’s relation to Jesus. Thus, we might add John the Baptist as a potential indirect witness to the virginal conception. More research needs to be done, of course, but this is a suggestion that needs to be fleshed out before it can be rejected outright. In particular, what needs to be examined are texts that speak with approbation about a certain holy leader within Judaism whose origins are known to be shameful. Further, those who speak thus must be godly themselves, good examples of the righteous man in Judaism. It would be interesting to find such parallels; if they exist, then my tentative conclusions here should be softened. But they should not be fully discounted because John’s view of Jesus seems to hint that he is someone very special, someone much holier than John himself, someone who is almost otherworldly. That effect cannot be explained on the basis of simply overlooking Jesus’ tainted beginnings. Some greater cause is required, something like the virginal conception.