There are may ways to define it and to account for it, but one way or another, and perhaps in a way that ultimately outstrips all accounts and definitions, something new emerges.  Something new emerges, and that which had seemed solid no longer seems solid.  The new relativizes the axiom, the foundation, the horizon.  Emerson was always thrilled about this - his essay on circles is his manifesto for the affirmation of becoming.  But we have to consider that this new emergence is perhaps value-neutral.  On the one hand, there is an ethics to not being reactionary, to being strong enough for it and so on.  But, especially now, it is not so obvious that the sheer novelty that explodes preconceptions and mores and so on is not ultimately a torrent of auto-destruction.  Or rather, it seems more likely that it is such a torrent.  It was Nietzsche who saw this clearly first: man will translate himself back into nature and destroy himself.  In 2016 there is a certain sense in returning to a more matter of fact, exoteric reading of Nietzsche as meaning what he actually says (as opposed to reading him through the lens of Klossowski and Deleuze and so on).  That said - even though blind affirmation is perhaps not the appropriate attitude towards the emergence of the new, it does call for some kind of ethics of affirmation: not the facile affirmation of capitalist decadence but the quasi-Christian affirmation of suffering that transforms pain into gratitude and a new horizon of meaning.  It is far too easy to mis-use the term "affirmation", which is, I think, used really in the latter sense by Nietzsche and Deleuze rather than the former, and to read them as meaning it in the former sense: being excited about new stuff.  For that reason, I replace the term "affirmation" with one that is more neutral: adaptation.