To summarise:

We’ve realised that objects affect each other somehow, and that’s as far as we’ve got—we haven’t postulated an “environment” yet. The prerequisite to the 3 steps of model development has been fulfilled: we’ve realised that there is a thing which is invisible, and we’re trying to deduce its properties.

Matt Webb, posted 2005-09-02 (talk on 2005-06-11)