If you assume that all meanings can be represented by a parse tree, then the claim here is straightforward - "Merge" is a constructor for a binary tree node, an

If you assume that all meanings can be represented by a parse tree, then the claim here is straightforward - "Merge" is a constructor for a binary tree node, and the claim is that Merge can construct any binary tree. I think the trickier question is whether parse trees really do capture everything about a sentence .. my guess is not.