G.A. Cohen argues that John Rawls' method of political philosophy--in particular his sensitivity to the facts of human nature--leads him inexorably to producing a nonideal conception of justice. In this thesis I defend Rawls against this accusation by demonstrating that the facts of human nature that he shows deference towards are a product of the "free development" of his ideal conception of the person. The result is that Rawls' conception of justice has the power and status that Rawls affords it, and that Cohen's critique fails to cause internal damage to Rawls' theory. My thesis is thus what the subtitle says it is: an essay in defence of John Rawls' deference to "human nature" from the "concessionary criticism" of G.A. Cohen.