Firstly it seems beyond doubt that Jesus spoke frequently of something called "the Kingdom of God", as implied by the prominence of the phrase in Mark and Q. According to the anti-apocalypticists, we should interpret this term not as the expectation of some future eschatological event (God literally imposing his Kingdom on Earth) but rather as a kind of by-word for Jesus' power over evil spirits (cf. Mt. 12:28; Lk 11:20) and his pursuit of divine justice. According to this view, Jesus believed that the Kingdom of God had already arrived, and that it resided (metaphorically?) within those who followed his example (Lk 17:21). However, it is clear that the term is not used exclusively in this way in the gospels, and such an interpetation appears to be too reliant on gnostic (and therefore later and de-eschatologised) interpretations of "Kingdom of God" (e.g Gospel of Thomas sayings 3 and 113). Given the inconsistency with which this term is applied, it is undeniably difficult to say with certainty which of the divergent meanings can be attributed to Jesus and which can be attributed to the Evangelists, but I think we have to view "the Kingdom of God" as referring to some future state that Jesus believed was already imminent. The phrase "the Kingdom of God has drawn near" can be found in both Mark and Q (Mk 1:15; Lk 10:9,11; Mt 10:7) and although the use of the perfect tense ("has drawn near") tells us that this process has already begun, the use of "near" clearly implies that it is yet to fully arrive.
Another example of imminent eschatological expectations within the early Christian community is that of the Lord's Prayer, which - by its distinctive use of the word abba (as I discussed above) - few scholars doubt can be traced back to Jesus. Here the exortation for God's Kingdom to "come" (Mt 6:10; Lk 11:2) again implies some future expectation, which Matthew further elaborates as arriving "on Earth as it is in Heaven". The imposition of divine will on Earth, with God arriving literally as a "King", is the very essense of an eschatological belief, and clear parallels can be drawn with the Jewish eschatologies of Jesus' time. Again, the anti-apocalypticists may demure that we needn't read eschatological beliefs into such passages and that in exhorting God's Kingdom to "come" Jesus was merely praying for some kind of divine justice, but even then it's difficult not to envisage this form of justice as necessitating some great eschatological shift.
For instance, Jesus is regularly portrayed as envisioning a future in which "the last will be first, and the first last" (Mt 20:16), where "the meek... shall inherit the earth" (Mt 5:5) and other similar reversals of fortune. This feature of Jesus' teaching - where the order of the current age is replaced with a new, completely inverted one as a consequence of divine intervention - is the very definition of an eschatological belief, hence the terminology given to such beliefs in the parlance of Biblical scholarship - inversionary ethical eschatology. Other elements of Jesus' ethics are so extreme ("if a man takes your shirt, give him your cloak also"; "if you want to follow me, sell all your possessions and leave your family" etc.) that its sometimes suggested that they could only be considered workable if we presume that Jesus thought they would only need to be followed for the short period of time before the eschaton. In any case, it's simply impossible to make sense of certain elements of Jesus' ethics without presuming some eschatological corollary.
Elsewhere in the Gospels, Jesus is regularly depicted as talking about "the Son of Man", an expression that is difficult to define precisely (in part because it is used in many different ways, both in the OT and the Gospels) but its use in the Gospels appears to be shaped by Daniel 7:13, an apocolyptic text. The term is used some 80 times in the Gospels, though the Jesus Seminar voted literally every instance of its use as either black or grey (meaning these sayings probably can't be traced back to the historical Jesus). This glib dismissal of an extremely well-attested tradition is based on the assumption that "the Son of Man" motif was a Christological title retrojected into the accounts by the Evangelists, who admittedly did frequently refer to the LXX for passages that they could apply to Jesus as they composed their Gospels. So, by this account, we should simply view the "Son of Man" passages as a consequence of OT prophecy-mining undertaken by later generations of Christians eager to find the most apt ways available to describe Jesus' nature.
But, of course, such explanations fail upon closer examination:
- Firstly, the "Son of Man" expressions are only
ever remembered as being spoken by Jesus and - therefore - were
presumably remembered as characteristic of his teaching. The "Son of
Man" does not appear anywhere else in the narratives of the Gospels.
- In contrast to other Christological titles ("Lord", "Christ",
"Son of God" etc.) Jesus is never given the appelation of the "Son of
Man" either in the narratives or by other characters in the Gospels. If
it was intended as a Christological title, it's difficult to explain why
it is almost never used that way, either in the NT or in other early
- Although Jesus is depicted as conflating himself with the "Son
of Man" in the gospels (especially when prefiguring his future suffering
and other soteriological themes) in the earlier traditions (namely Mark
and Q) Jesus often seems to be clearly referencing this "Son of Man" as
a third person, invoking him in an eschatological context (see Mk.
8:38; 13:26; 14:62; Lk. 12:8,10,40). This is the inverse of what we
should expect to find if the "Son of Man" motif was a consequence of
later Christological theorising. (The anti-apocalyticists partially
attempt to explain this away by suggesting Q was composed in three
layers, with a sapiential layer being penned first and the apocalyptic
layer coming only later. Such a precise layering of a still hypothetical
document stretches the evidence too far, and is too dependent on
comparisons with the likely much later Gospel of Thomas.)
- Possibly the most important bit of evidence against the idea that the "Son of Man" motif was a retrojection into the tradition by later Christians is that these later Christians seem almost completely oblivious to it. The Gospel authors seem confused by its meaning (does it refer to Jesus or some third person?) and the term appears just three times in the NT outside of the Gospels-Acts complex (Heb 2:6; Rev; 1:13, 14:14), and even then only in an eschatological context recalling Dan 7:13. If the "Son of Man" is the result of later Christian thought, why doesn't it ever seem to appear in said later Christian thought?
Speaking of Christian thought, the prominence of eschatology from the very first Christian writings is also very difficult to explain if it cannot be traced back to Jesus. Paul writes expansively on explicitly eschatological themes like the parousia, a generalised resurrection of the dead, the coming of a "new age" (in contrast to the current "evil age") and the arrival of God and his angels on Earth in future judgment of the human race, and these themes are present from his earliest writings, barely 20 years after the death of Jesus. What is more, it must be stressed that such ideas were comprised of imminent eschatological expectations.
The fourth chapter of 1 Thessalonians makes it quite clear that Paul expected the intervention of God in the affairs of the world very soon, and that at this moment the faithful "will be caught up in the clouds together... to meet the Lord in the air" (4:17). Similar eschatological urgency can be noted in 1 Cor 7:29-31, and can be inferred from other scattered passages throughout his epistles. The fact that such predictions ultimately failed to manifest themselves can be posited as one of the major motivations for later authors forging epistles in Paul's name.The "contested" Pauline epistles (2 Thessalonians, Colossians, Ephesians) all contain aortist subtexts (that is, the belief that the eschatology had already been realised), and relevant passages are not difficult to adduce (e.g. 2 Thess 2:2; Col 1:13, 2:12-13, 3:1; Eph 1:4; 2:5-6). In Paul's corpus as in the gospels, then, it seems relatively clear that the most urgent eschatological exhortations come from the earlier material, with the more circumspect or anti-eschatological material being composed later.
So where could he have gotten such ideas from, if not from the tradition surrounding Jesus? The Pharisees (the Jewish sect of Paul prior to his conversion) didn't share such eschatological beliefs, at least in the context of resurrection. Given that, it's difficult to see where Paul could have inherited his eschatology from if not from the early Christian community, and it's difficult to see where they could have got their eschatological beliefs from if not from Jesus.
As noted above, the eschatological themes are strongest and most urgent in the early gospel layers of Mark and Q - i.e. those dating closest to the life of Jesus. The urgency of the situation was apparently such that Jesus is depicted as saying (at the conclusion of the so-called "Little Apocalypse of Mark 13) that "this generation will not pass away until all these things have taken place" (Mk 13:30; cf. Mk 9:1) and in Q the eschatological situation is depicted by Jesus as being so urgent that apparently a mourning son doesn't even have time to bury his father (Mt 8:21-22; Lk 9:59-60)! After decades of apparently unrealised eschatological expectations, why would the gospel authors have been moved to place such expectations on Jesus' lips with such embarrassing and unnecessary urgency if they cannot be traced back to him? Note also that the truly late books of the NT (i.e. gJohn, the Pastoral Epistles) contain almost no eschatological themes, further evidence against such themes being a later Christian development.
So if we can presume as well that John the Baptist had an eschatological theology (as the Gospels indicate - Mt 3:2,7; Lk 3:3,7) then it seems that Jesus is sandwiched on either side by strong eschatological beliefs. The most natural fit for this data is that eschatological teachings were a common feature of John's teachings, which Jesus inherited and passed onto his own followers, who wrote about them at length, before they were slowly softened or abandoned by later generations of Christians as the expectations remained unrealised. It's difficult to coherently explain this data if we assume that Jesus' teachings were not in a large part defined by his eschatological beliefs.