Once again I find myself thinking along the same lines as Mark Hannah. I guess great minds think alike...
Anyway, I think that Quintillian is much too hard on the rhetorical use of what somebody else might have said, or mimesis. To me, there are two kinds of genius in the rhetorcial arts: those of inventive (Epistemic)ways of making knowledge, and Interpretive which is relating to, involving, or providing an interpretation or explanation of knowledge. Both can be equally valuable ways for students to use writing.
I think we are far too hard on interpretive schemes lately. Mimesis can be a valuable way to make sense, and critique diffiucult texts, and a valuable tool in the learning process because it allows the writer to enter into the tradition, interpret it, and remake it. In true mimetic writing you are not making new knowledge so much as remaking or reevaluating old knowledge. Interpretation cannot neccesarily :relating to, involving, or providing an interpretation or explanation of something "make" knowledge. It works from a much different cognitive framework than inventive writing.
The problem, which Quintillian so succinctly points out, is "imitation is not sufficient of itself, if for no other reason than that it is the mark of an indolent nature to rest satisfied with what has been invented by other" (132). This is true. Interpretation of a text has to move beyond a "cliff notes" reading of a text, and move beyond summary toward analysis of synthesis.
Quintillian reinforces this by stating, "Even those who do not aim at excellence should rather try to excel, than merely follow, their predecessors" (133). However, I find myself wondering what Pseudo-Longinius would say in response to this. He states, "They put their trust in the maxim "failure in great attempt is at least a noble error" but evil are the swellings, both in the body and in diction, which are inflated and unreal, and threaten us with the reverse of our aim; for nothing, say they, is drier than a man who has the dropsy" (78).
To Longinius one's reach should not exceed his grasp. If you cannot write truly subliminaly then you should not try, but I also know that Robert Browning argues the opposite stating, "Ah, but a man's reach should exceed his grasp -- or what's a heaven for?"
I think this is the basically split in writing studies right now. Should we always strive to CREATE knowledge, or interpret knowledge. I don't see why it has to be one or the other.