The simulation argument is an interesting intellectual exercise, and I'd charitably expand the definition of such simulations to universes of an artificial nature in general, but it's still just a thought experiment about something which cannot be falsified. Granted, it's a fascinating one, but it shares too many traits with <i>The Invisible Dragon in my Garage</i> to be of profound scientific value.<p>It's worth taking into account that people tend to have two entirely separate ideas about the nature of any such simulation.<p>The first one is a Matrix-like universe: a world designed from the ground up to be an illusion specifically for us - a computer program so idiosyncratic as to be utterly implausible, which only cares about deceiving human minds into living in an artificial environment. This is the concept of a computer simulation always invoked by the popular media whenever this subject comes up.<p>The second one, which is what scientists usually mean, is an actual simulation that merely runs the basic processes of physics from which all the other things in the universe emerge - and these include accidentally, among other things and quite marginally, intelligent life forms such as humans. It's merely an uncaring physics simulation indistinguishable from a "natural" universe.<p>In the end both of these are scientifically barren concepts. The Matrix is an implausible just-so story with quasi-religious undertones, and it's a concept that exhibits quite a few glaring holes the closer you look at its practical implications - holes which seem like they are in disagreement with daily observation and hence should lend themselves to falsification. The cold physics simulation on the other hand, while it doesn't share the intellectual weaknesses of the Matrix, gets us rapidly to a point where we might ask what difference it makes at all whether the fabric of reality is running on an artificial or "natural" substrate if there is no hope of ever finding out.