Can there be a global, interesting, coherent constructivism about practical reason?

More and more people seem to think that constructivism - in political philosophy, in moral philosophy, and perhaps in practical reasoning most generally - is the way to go. And yet it is surprisingly hard to even characterize the view. In this paper, I go to some lengths trying to capture the essence of a constructivist position - mostly in the realm of practical reason - and to pinpoint its theoretical attractions. I then give some reason to suspect that there cannot be a coherent constructivist view about practical reason as a whole, at least not if it is to be interestingly constructivist, in a sense I make reasonably precise.