Today I noticed the similarities between Luke 14.11 and 18.14. The Greek is nearly exact: hoti pas ho hupswn eauton tapeinwthedetai kai ho tapeinwn eauton hupswthesetai (14.11; cf. 18.14, where kai is replaced with de): "Because everyone exalting himself will be humbled, and the one humbling himself will be exalted."
I immediately considered the possibility that the two pericopes of Luke 14.7-11 and 18.1-14 are describing the same thing, or that Luke's Jesus is making the same point regarding the same people. But I was drawn away from that venture by another proposal. (I intend to investigate such a possibility very soon.)
These statements are of a certain kind, of a certain form. I continued searching the rest of Luke's Gospel and noticed a kind of trend regarding such forms. In Luke 8.18, we find the statement, "For to him who had will more be given, and from him who has not, even what he thinks he has will be taken away." So far as I can tell, this is the first statement of this kind, using this rhetoric, in Luke's Gospel. From there, I moved forward through the Gospel looking for similar rhetorical structures. I found these (including 8.18, 14.11 and 18.14):
8.18: For to him who had will more be given, and from him who has not, even what he thinks he has will be taken away.
9.5: Wherever they do not receive you, when you leave that town shake off the dust from your feet as a testimony against them.
10.6: If a son of peace is there, your peace shall rest upon him; but if not, it shall return to you.
10.16: He who hears you hears me, and he who rejects you rejects me, and he who rejects me rejects him who sent me.
11.23: He who is not with me is against me, and he who does not gather with me scatters.
12.48: Everyone to whom much is given, of him will much be required; and of him to whom men commit much they will demand the more.
13.30: Some are last who will be first, and some are first who will be last.
14.11: Because everyone exalting himself will be humbled, and the one humbling himself will be exalted.
16.18: Everyone who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery.
18.14: Because everyone exalting himself will be humbled, but the one humbling himself will be exalted.
20.18: Everyone who falls on that stone will be broken into pieces; upon whomever it falls, it will crish him.
(If I have forgotten any similar cases, please make them known.)
It seems to me that Luke is moving from a more primitive rhetorical form to a more developed one. Each of these cases is 'tighter' in verbal form than the previous case (with the lone exception of the 8.18, which looks much closer to the last four verbally that any one case between them.) I intend to study these passages in order alongside the other Synoptics, and even alongside John. But, should there be something to this, two things emerge:
1. Richard Anderson has suggested that Luke uses a "step progression method" in telling his story (http://kratistostheophilos.blogspot.com/2007/01/step-progression-method.html). Perhaps he is right, and this development of rhetorical form might help establish that.
2. If Luke is developing these sayings as he goes along, making the form stronger and tighter, perhaps this is a reflection of a free mind and a free hand. If so (which I'm not sure can be proven), perhaps this is evidence that Luke wrote without depending on a written source. If it can be shown that Luke's redition of these statements, when taken together, is less developed compared to the other Synoptics, perhaps this is a step toward strengthening Lucan priority.