The "Conceptual Persona" is an inevitable product of the yet-unproven theory of immanence.

A large part of my problem with D&G's second chapter is that it seems forced by chapter three.  What I mean is this -- they were almost certainly committed to the ideas of immanence and the plane of immanence before they started writing chapter two.  Once we accept immanence, the idea of the autonomous conceptual persona virtually writes itself.  That doesn't mean that it's the correct model of reality; it's validity rests on that of immanence itself, which has, as of yet gone unproven.

When Descartes, for instance created the cogito, he almost certainly did not concieve of "the Idiot" (itself a moniker applied later) as a conceptual persona.  I believe this, because Descartes, like the vast majority of historic Philosophers believed in transcendence.  If we were to take a transcendent bearing with respect to the Idiot, we could very easily characterize Descartes as the "creator", and the Idiot as a step in his thinking process, functioning essentially as a premise in the proof for the Cogito.  To say, as D&G do, that Descartes could not reach the Cogito without the Idiot is true, but only in the sense that a proof without a necessary premise isn't a functioning proof at all.  To say that the Idiot has autonomy apart from Descartes' will that allows it to do things that Descartes cannot is absolutely absurd.  The Idiot -- all of its choices, its goals, and its ultimate end -- are products of Descartes, not of the Idiot's own autonomy.  No, Descartes can't actually doubt away all of his beliefs, but he can explore the possibility in his head.  The Idiot is just a tool in this process, something that Descartes wields as he shapes the Cogito from other concepts, concepts that, incidentally belong to Descartes' memory, not the Idiot's.

This model is so simple, so natural that I think we have to ask why D&G take the tack that they do, fighting for the autonomy of the conceptual persona.  I think it is because they cannot do otherwise while remaining committed to the idea of immanence.  To take up the simple model of thought that I have framed above, they would have to admit of a "creator" and "created" distinction, which they absolutely cannot do while advancing the idea of the plane of immanence.  Therefore, the Idiot (and all their other examples of conceptual personae, for that matter) must exist on the same plane as the end-concept's "signer" and the concept, itself.  After we understand what D&G want to say in chapter three, chapter two must read the way it does.  If D&G want me to take chapter two or three seriously, they are going to have to better explicate the reasons for me to buy into immanence.  As of now, it doesn't click with me, despite my outside reading.  The transcendence model is so much more natural to me, and What is Philosophy? has not given me the slightest reason to feel differently.