The Parity Principle 1

Chalmers recently suggested in comments here that more attention might be paid to the Parity Principle as a means of arguing for EC.  Mike Wheeler is, I think, doing this in his current book project Extended X.  And Sven Walter also has a paper where he is developing other versions of the principle in an effort to show that there is a kind of pro-EC bias in the current formulation.  Shannon Spaulding also has a paper discussing this.