Relatismo (my made up term for this emerging philosophy) says that two events are only different if they have different past lightcones, different past histories. Or as Smolin puts it, different VIEWS. You and I are different people only if we come from different cities or neighborhoods and had different experiences with girls and saw different movies and so on. If every detail in our past is the same, even down to our record collections, then (sorry about this) we are the same individual. As I see it, the central relatista message in "The Case for Background Independence" is on page 33, in a passage which is extracted here from context and quoted first in isolation. --key passage in isolation-- Julian Barbour and I call a spacetime in which the view of each event is distinct a Leibniz spacetime. We note, with some wonder, that the fact that our universe is not completely in thermal equilibrium is due to the fact that gravitationally bound systems have negative specific heat, and therefore cannot evolve to unique equilibrium configurations. Furthermore, gravity causes small fluctuations to grow that would otherwise be damped. This is why the universe is filled with galaxies and stars. Thus, gravity, which as Einstein taught us is the force that necessarily exists due to the relational character of space and time, is at the same time the agent that keeps the world out of equilibrium and causes fluctuations to grow rather than to dissipate, which is a necessary condition for it to have a completely relational description. --end quote-- I am not sure why one can say Einstein taught us gravity is the force that necessarily exists due to the relational character of space and time--it sounds like the germ of an idea and I guess it has to do with the equivalence principle. Maybe someone can explain it, or if I think some more about it I'll understand. the business about negative specific heat is straightforward. Picture something like a globular cluster, even better a globular cluster of smallish iceball comets. Like a cloud of gnats, gravity-bound. If you can inject energy into the cluster, so it swells out IT GETS COLDER because things move slower---the way outer planets move slow and Oort cloud comets move even slower----so pumping energy into the cloud makes it expand and cool (less kinetic energy = less temperturature). Astronomers say "virial theorem" (Latin vis, viris, energy, strength) this knowledge of the NEGATIVE SPECIFIC HEAT of gravitybound systems is several centuries old which is why it has an old name. If you can bleed energy out of the cluster somehow, it gets HOTTER in the sense of their moving faster. Indeed if you can bleed enough energy out of a cloud of cold comets they can even pile together in a heap at the bottom of their own well, and form a star, and get REALLY hot. So gravity-bound systems work the OPPOSITE of systems we are used to where putting energy in makes the temperature rise and bleeding energy out makes the temperature fall---that is a positive specific heat and that is always what we expect. a bunch of things with pos specific heat will get into equilibrium the hotter ones will radiate heat and cool off, and the colder ones will receive radiant energy and warm up, till everything is the same temperature. gravity things dont come to equilibrium like that because the things that radiate away some of their energy get HOTTER as they lose and the things receiving energy get colder as they gain ACCIDENTAL INEQUALITIES TEND TO GET MAGNIFIED by gravity. minor kinks (instead of automatically smoothing out) become major. At least until everything is in the form of black holes. I can't picture it beyond that. Or else until everything is RADIATION and no longer gravitationally bound. But that is looking too far into the future. The main thing is that the way things are now the gravitationally bound systems have negative specific heat and gravity does NOT CONDUCE TO UNIFORMITY and equilibrium and keeps everything in an uneven clumped and clustered very hot here very cold there disequilibrium. and gravity is unusual this way. other kinds of systems are more likely to show positive specific heat and to come to ordinary evened-out equilibrium. Now I think a relatista would say that it is this UNEVENNESS of the universe that allows so many different past lightcones or past histories and thus allows so many distinct spacetime events. According to extreme relatismo, the reason that the universe can have so many distinct spacetime points, called "events", in it is that gravity does a very good job of making the universe LUMPY and uneven and totally un-symmetrical. The universe has no symmetries, whew! what a relief! thank your lucky stars it has no symmetries because otherwise things wouldnt have UNIQUE IDENTITY from having different relations to their surroundings and different causal past histories. Don't say thank goodness, say THANK GRAVITY. this is a risky thin-ice idea. It hasnt really been figured out yet by anybody, I suspect. At any rate for me it is just the thin bare beginnings of an idea. Like someone you pretend not to notice because you are both reading your books, but actually do notice. I will quote the same passage now, but in context.