Alan Kay, delivering the keynote speech at the Second West Coast Computer Faire in 1978 said, ``we decided to focus on simulation in Smalltalk, because that's the only really interesting thing to do with a computer''. When I heard this, I was aghast: ``Simulation'', I thought, ``why in the world would people want to use personal computers to model throughput in a machine shop, or to calculate the number of toilets in a football stadium''. Certainly any rational person wanted a personal computer to do real computer science on it: to write operating systems and compilers so that others could use them to write programs, and...well, I hadn't thought that out completely.
``Simulation'' had come to mean (at least in the computer science lexicon), a specific kind of modeling of systems, usually done in an odd simulation language such as Simscript or Simula. What I only realised years later was that what Alan Kay was talking about something far more grandiose when he said ``simulation'': getting the whole wide world into that itty-bitty can: the computer. And yet, ``simulation'' in the limited computer science sense has already had a great and often little-appreciated impact on computer science as a whole. In his speech, Alan Kay exhorted people to look closely at Simula-67 for the direction of the future. Simula-67 included (in 1967!) classes, object orientation, multiple communicating processes, in fact close to a laundry list of what is currently considered the way to approach complex problems. So simulation in the small has already influenced the mainstream, and I believe that simulation writ large will have an impact many times greater.