  Working scientists sometimes describe simulation studies in experimental terms. The connection between simulation and experiment probably goes back as far as von Neumann, who, when advocating very early on for the use of computers in physics, noted that many difficult experiments had to be conducted merely to determine facts that ought, in principle, to be derivable from theory. Once von Neumann’s vision became a reality, and some of these experiments began to be replaced by simulations, it became somewhat natural to view them as versions of experiment. A representative passage can be found in a popular book on simulation: