Actually, Kunnigunde's smart question exposes the Achilles' heel of the Q theory. If Q postdates Mark, it can be shown to be a redundant hypothesis (by applying the Farrer's test). I think one of the least understood aspect of the Q-noQ dilemma is the inter-relation of Mark's narrative and the putative Q sayings. One example would be the start of Mark's gospel, the assumed Q verses 3:2b-3a (the introduction of the Baptizer), Q3:7-9 and their relation to Mark 1:4-5. One obvious possibility - to those not welded to Q - would be that the Q3:7-9 sayings are simply a literary dramatization of Mark's verses just like later the Temptation in the desert. If you follow this as a hypothetical scenario then the John's Q preaching of the one to come (Matt 3:11-12, Lk3:16b-17) can evidently be read as dependent on Mark 1:7-8. Obversely, if one accepts the reality of Q, then logically Q must have preceded Mark and him draw on that tradition, since it is now nearly universally accepted that both Matt and Luke knew Mark, and therefore, Matt could have drawn on Mark when prettifying the Baptizer's introduction and then Luke (nearly) copying Matthew as the superior rendition.Ben C. Smith wrote:I do not have any example (at least none relevant to this discussion). The overall observation does not depend on Q either predating or postdating Mark. It deals merely with how Luke and/or Matthew treated Mark and the Q material.
(My mind is still very much not made up about the relative order of the Marcan and the Q material.)
Best,
Jiri
PS. Despite the problem of Luke's re-structuring Matt's narrative, I believe it nearly certain that Luke knew his version of the gospel (to a large degree because of Lk 4:22 slight variation of Matt's 13:55 substituting "not Joseph's son" for "not the carpenter's son"), and modified it to suit the purposes of his community.