If you might be living in a simulation then all else equal you should care less about others, live more for today, make your world look more likely to become rich, expect to and try more to participate in pivotal events, be more entertaining and praiseworthy, and keep the famous people around you happier and more interested in you.

This is the table of contents and first chapter of Physics Meets Philosophy at the Planck Scale (Cambridge University Press, 2001), edited by Craig Callender and Nick Huggett. The chapter discusses the question of why there should be a theory of quantum gravity. We tackle arguments that purport to show that the gravitational field *must* be quantized. We then introduce various programs in quantum gravity and discuss areas where quantum gravity and philosophy seem to have something to say to each (...) other. (shrink)

I argue that at least one of the following propositions is true: the human species is very likely to become extinct before reaching a ’posthuman’ stage; any posthuman civilization is extremely unlikely to run a significant number of simulations of its evolutionary history ; we are almost certainly living in a computer simulation. It follows that the belief that there is a significant chance that we shall one day become posthumans who run ancestor-simulations is false, unless we are currently living (...) in a simulation. I discuss some consequences of this result. (shrink)

An assessment is offered of the progress that the major approaches to quantum gravity have made towards the goal of constructing a complete and satisfactory theory. The emphasis is on loop quantum gravity and string theory, although other approaches are discussed, including dynamical triangulation models (euclidean and lorentzian) regge calculus models, causal sets, twistor theory, non-commutative geometry and models based on analogies to condensed matter systems. We proceed by listing the questions the theories are expected to be able to answer. (...) We then compile two lists: the first details the actual results so far achieved in each theory, while the second lists conjectures which remain open. By comparing them we can evaluate how far each theory has progressed, and what must still be done before each theory can be considered a satisfactory quantum theory of gravity. We find there has been impressive recent progress on several fronts. At the same time, important issues about loop quantum gravity are so far unresolved, as are key conjectures of string theory. However, there is a reasonable expectation that experimental tests of lorentz invariance at Planck scales may in the near future make it possible to rule out one or more candidate quantum theories of gravity. (shrink)

The quest for an all-encompassing theory, finally intended to give a solution to the problem of the unification of all natural forces, is seen today as one of the most important objectives of theoretical high-energy physics. This so-called 'Theory of Everything' is, actually, identified by some theoretical physicists with superstring theory. But superstring theory is in a crucial way incomplete. And, above all, it has fundamental problems with empirical testability – problems that make questionable its status as a physical theory (...) at all. (shrink)