 at least three levels removed from the physical world that they try to represent. That is, first (a) we stylize physics into differential equations, then (b) we force these equations into the mold of discrete space and time and truncate the resulting power series, so as to arrive at finite difference equations, and finally, in order to commit the latter to algorithms, (c) we project real-valued variables onto finite computer words (“round-off”). At the end of the chain we find the computer – again a physical system; isn’t there a less roundabout way to make nature model itself? (Toffoli 1984: 121)