[QwOpHGyZ]

Part of what I was going to say earlier... in the OP, the example that the katana won't cut steel, yet Reiku discovers that's not true... really, the original assumption is more like what we would call 'common knowledge' (which may or may not be true), rather than common sense. Common sense usually refers to something that is obvious... for example, "If your knee is injured, don't run too hard on it - it's only common sense", or "It's common sense to iron your shirt before you have an interview"... also may I add, common sense seems to be noteable by its absence (even we have a saying in England, "Common sense is not so common!"), for instance, you can often think of an example that someone perhaps ran hard on their injured knee and made it worse, or didn't bother to iron their shirt, or something like that... and people will look and say, "Why didn't you use your common sense?!" meaning why didn't you do the obviously sensible thing?!

I did have a more articulate way of putting it, but I can't do all my rethinking of my first post again, my brain is too tired...