Alterity is a philosophical conceptual construct by Jean Baudrillard. When one experiences a near death experience and survives, the two "selves" continue on a parallel path that gradually continues parting/continuing to diverge through life. The film Another Earth with Britt Marling is a perfect illustration of what Baudrillard means http://moviesandfilm.blogspot.com/2011/09/review-another-earth-at-moxie-in.html This corresponds to Pirsig's Phaedrus who is electro shocked into alterity as another person as if just being born with no memory before this new moment.
Irreversibility is Baudrillard's great contribution to philosophy. To fully understand his work one must understand he is Nietzschean in blood and bone. Pirsig never mentions Nietzsche once, yet he breathes through this novel. As of course do Foucault and Baudrillard. It is rare than a Foucauldian thinker moves into Baudrillard (Ayn Rand does but is misread by her disciples). Pirsig is so clear with his continuing binary that he cannot come to terms with easily at all. He is not aware of how Baudrillard has separated the Symbolic Order from the Order of Production (Pirsig's classic and romantic methods of thinking/ reasoning). But there it is, clear as day, the two orders that are separate, the territory and the map as Borges calls it. Or as Jesus does when he overturns the tables of the money changers in the temple, separating the sacred from the worldly. (I am not using profane as that concept has different resonances I don't want to get into.)Two parallel orders that comprise the world. This conceptual construct can be read through Plato of course also, the REAL and the shadows in the cave. The Order of Production is IRREVERSIBLE. From this capitalism metastasizes like cancer cells (Marx). The Symbolic Order is REVERSIBLE and these terms are Baudrillard's great contribution according to Simon Critchley. If you want examples I have blogged many of them so ask if you want more on this and I will link you. DeLillo is especially perceptive on this in Cosmopolis.
But these two terms are philosophical constructs. In Fountainhead we see Gail Wynand is unable to reverse The Banner as it has become firmly planted in the Order of Production. He cannot use it to turn Roark into a hero, a true artist, because Toohey has taken control in homeopathic doses, substituting the territory of journalism into the map of propagandizing. What is left for him finally is to destroy The Banner completely. And that is Nietzsche, excess is required to end what must be stopped so that it implodes.
Pirsig's excess on his road journey is also in the Symbolic Order and the Order of Production. The physical trip on the motorcycle and the "trip" in his mind as he pieces his lost fragments of his lost self knitting them together with his present self, his present Alterity. Of course it can be read through the interpretation of Freud's thinking, or even Jung's, but I prefer to stay with Foucault and Baudrillard and not take the swampy, sinking path into interpretation from which it will be impossible to get out of and will force Pirsig back into the Dialectic which he has so brilliantly led us to escape from.