If I had to debate flat earthers, which thankfully I do not, I wouldn't try to "reason" with them. Instead, I would bring in several maps using different kinds of projections and ask these questions:
- Where's your map?
- If they are the same as my maps, what happens at the "edges" of my maps?
- If your flat map is finite, what happens at the edges?
- If your flat map is infinite, where is the boundary between the known and unknown worlds?
These questions would form the basis of my engagement. Unless flat earthers provide answers to all these questions they aren't actually saying anything at all.
Discussion
The first question disposes of the "moving goal posts" problem. The second refutes attempts to use "real" maps. The last two questions make it impossible for flat earthers to ignore the boundaries that must exist in a flat map.
This strategy avoids getting bogged down in what I call "bozo epistemology". Instead of attempting to prove that facts are facts (which is impossible!), we merely insist that flat earthers be clear about what they would have us believe.
It would also be reasonable to take a globe, and demand that flat earthers explain where it is in error. The globe represents distances, directions and areas. It is up to flat earthers to "falsify" the globe.
Summary
The question, "where's your map, and what does it mean?", poses an impossible problem for flat earthers.
The "Where's your map" challenge might apply to other bogus ideas and the crackpots and liars who espouse them. Alas, it's much easier to assert that the earth is flat than it is to refute it. In other words, the ideas presented here have little or no practical value.
Edward