Anderson's latest is to argue in a circle.

I've basically got Anderson right where I want him and I'm glad that Spencer was able to draw this out in public. Recently, Anderson accused Spencer of not "affirming" very basic distinctions and so concluded that he wouldn't (consistently) be able to evaluate any argument--so Anderson concludes, no point in discussing any further. To that, Spencer responded:

@Owen Anderson Since we both believe that 'a is a' applies to reality, the questions now seem to be, why think that we must have clarity of basic distinctions to have intelligible discussion in the first place? This is your assumption, but it's not obvious that you're right. Perhaps our basic distinctions are ultimately grounded in our shared intuition, and nothing (epistemically) more. If we lack clarity at the basic level, why do you insist that discussion is impossible? Do you have an argument? (Note: I'm open to there being clarity at the basic level, if you can show it.) 

In addition, why do you insist that we must have clarity of basic distinctions to have knowledge?...

The point here is that they are not disagreeing over whether 'a is a', but rather whether we need to be absolutely certain that 'a is a' if we are to be able to consistently evaluate arguments (and thus have rational grounds to continue the convo).

So Spencer, rightly asks Anderson to prove his view that merely believing in basic distinctions is not enough. That is, he's asking Anderson (as I have before) to prove the claim that we must have certainty of basic distinctions if we are to have intelligible discussions, and consistently evaluate arguments. To that, Anderson replied,

@Spencer Hawkins You said "why think that we must have clarity of basic distinctions to have intelligible discussion in the first place?" Perhaps basic distinctions aren't clear, including the distinction between agreeing and disagreeing, and really these are just the same thing. If so there isn't much left to discuss. (Emphasis mine).

It boggles my mind that Anderson would think this is a sufficient response. He's not a dummy. Again I don't know which is the more charitable reading of the situation--is he just that ignorant when it comes to questioning his basic assumptions? Or is he knowingly presenting bad arguments with the hope that people won't call him out on it?

True, if one doesn't affirm with absolute certainty that 'a is a', then it follows trivially that by one's lights, it's remotely possible that "agreeing" is "disagreeing" for example. So, "perhaps" agreeing is disagreeing. That much is granted by all parties. But why should anybody think that it follows from this that "there isn't much left to discuss?" This is extreme reasoning if not melodramatic. It's like telling someone that consistency demands they never get on an airplane as long as they believe it's at least possible that it could crash (and provided they don't have a death wish).

There's nothing about "it's possible that agreeing is disagreeing" that logically entails that there is no room or point in further discussion. Consider:

(1) It's possible that even our most basic distinctions do not reflect reality. 

(2) Therefore, we have no way of evaluating arguments, (i.e., discussions are pointless). 

Spencer is asking Anderson to prove that (2) follows from (1) and Anderson's response is to restate that it does! That's textbook circularity!

In fact, it's not even clear how one would go about proving that (2) follows from (1). It's not like the very meaning of (1) is just the meaning of (2) so there isn't an analytical relation. So how does Anderson know with certainty that the entailment which he merely presupposes, holds? That's the challenge.