Begging your indulgences, RecoveringYuppy, MEequalsIxR, et al. ... I'd like to add something which addresses surmises made be hecd2 and W.D.Clinger (and which some others - e.g. Dave Rogers, The Man - may also find interesting).
If markie (or optiongeek) had taken up my step 1, what had I planned next, then, etc?
A perhaps somewhat surprising answer: it would have depended ... on how markie had addressed my initial question.
I hadn't thought it all that likely that we'd start by exploring "
infinitesimals", but was certainly prepared for this at some point (ha!). By setting the point charge outside the ring, I was prepared to explore symmetry, look at how to integrate all points on the ring, work on the concept of force being a vector, how to derive net force, see if a ring could be reduced to/made the equivalent of a point (net force the same? or not?), extend to a sphere (would have to have made sure symmetry was covered first; this could also be where optiongeek's question was considered), ... and only after all this, move the point charge to inside the ring/sphere.
However, the order of these (to some extent), and whether other things would have been covered (first, or later), would have depended on how markie responded, at each step. The biggest challenge I thought would be calculus and/or limits; my impression is that markie has a poor grasp of these (optiongeek seems to have an even weaker grasp), and neither is easy to work out on your own (for those who like this sort of thing, Lakatos, in his "Proofs and Refutations" explores some of the history somewhat analogous to this; from memory, it took mathematicians several hundred years to get fully rigorous!

).