He understood that the task of molding the incoherent and dizzying stuff that dreams are made of is the most difficult work a man can undertake, even if he fathom all the enigmas of the higher and lower spheres -- much more difficult than weaving a rope of sand or minting a coin of the faceless wind.
-- from "The Circular Ruins" by Jorge Luis Borges
Christopher Nolan's Inception is another one of those sci-fi tales confronting the problem of infinity lurking behind subjectivity. Because it uses dreams instead of virtual reality, the film is structurally closer to the short story quoted above than the cyberpunk-influenced Matrix (although the action puts it closer to the latter). In Borges' tale, a sorcerer spends years dreaming a man into reality only to learn that he, too, was given life via the same method. And it's just as likely that the dreamer of the sorcerer is himself being dreamed, etc., ad infinitum. This is the old phenomenological problem of the Transcendental Ego.
In order to have a collection of intentional states (which are always regarding some mental or physical object) cohere as a self (the 'I' that's doing the believing, desiring, etc.), Edmund Husserl posited a transcendent pure subject that couldn't be objectified. This I was pre-reflective, the guy who was there each time an intentional state was being reflected upon (the I thinking "it is I who likes pizza" at one time and "It is I who hates the rain" at another). As with all such metaphysical "buck stops here" explanations (cf. the final cause argument for God), the question soon arose as to why this Ego didn't require another, more transcendent one to ground its reflective relations. And since then, many theorists from various disciplines have been perfectly happy with the notion of a fractured self, that the I is nothing but a comforting mask for deterministic forces (cf. the death of the author, social Darwinism, or connectionism). Causal language is more scientistic, but problematic for suggesting the possibility that we humans have free agency, that there is something of a self not purely reducible to objective control, or material determinations. Thus, philosophical libertarianism sounds suspicious to many, like a new agey charlatanry.