As I noted in the previous thread, I can tell (sometimes) that I'm rationalising, even if my conclusion does turn out to be correct - it's a matter of arriving at a belief by a bad process. (In my case I get my polemicist on even though there's a little voice in my head noticing that my epistemology isn't quite justified. This is harder to notice because my output looks much the same those times I consider that I really do have my epistemological ducks in a row - I have to notice it while I'm doing it.)