Question

I listened to your latest podcast, where you attacked postmodernism by saying that the implications of the theory are that you end up with a collection of narratives that do not communicate with one another. 
And I wondered: is that really an argument against postmodernism?
Because that is exactly what they maintain: there is no single truth, and narratives indeed do not communicate.
Or perhaps, to phrase it in the spirit of the latest column: this is begging the question. You assume that narratives are supposed to speak to one another, and therefore you argue from that. The postmodernists do not assume that; quite the contrary!
In addition, if this really is an argument against it, why is it relevant? If the postmodernists are right that there is no single truth, then what can be done? Arguments really are empty of content. That is simply an implication of reality.
Shouldn’t an attack on postmodernism have to demonstrate that there is one truth? For example, that just as 1+1=2 (I understand that they agree with that), so too there is an ideology / morality / outlook / philosophy that is closer to the truth than another one?