Two philosophical ideas motivate this paper. The first is an answer to the question of what is an
appropriate activity for a physicist. My answer is that an appropriate activity is anything where
the tools of a physicist enable him or her to make a contribution to the solution of a significant
problem. This may be obvious in areas that overlap physics (e.g. chemistry, engineering, geology)
but also true in any endeavour where mathematical modelling may contribute insight to the solution
of problems (e.g. timing of traffic lights, efficient ways to seat passengers on airplanes, whether
it is better to walk or run in a rain shower). The second idea concerns an approach to problem
solving. Before some people try to solve a problem, they think they first must learn everything that
is known about the subject. However, sometimes an effective approach is to declare, ‘I’m going to
solve this problem with what I know now!’ I see a relationship between this approach and the idea of
back-of…