Main Question or Discussion Point
Which do you consider to be a better foundation for some system of (axiomatic) beliefs: a circular argument, or one with undefined terms? Take Newton's laws for example, we can either say "an inertial frame is one in which Newton's laws hold, and Newton's laws hold in an inertial frame", or we can leave an inertial frame undefined. I remember reading that the mathematician Weyl went back to redo much of the logician Frege's work, because he was unhappy with his use of recursive logic as a foundation. Any thoughts?