30 Pages Posted: 8 Aug 2013

Date Written: 2013

Abstract

Must principles of justice be practical? Some political philosophers, the “implementers,” say yes. Others, the “idealists,” say no. Despite this disagreement, the implementers and idealists tend to agree that what it means for principles to be practical is that they are successfully implementable with fairly predictable results. In this paper I argue that both sides in this dispute are mistaken, each guilty of epistemic overconfidence. By accepting the demand that principles of justice be implementable, the implementers have too much confidence in our ability to determine, in advance, the limits of what is practically possible. By rejecting the idea that principles of justice need to be implementable, the idealists have too much confidence in our ability to determine, in advance, what is normatively desirable. I argue that we should adopt an alternative conception of practicality, one which speaks to the core concerns of both implementers and idealists, reconceives the roles of ideal and non-ideal theory, recognizes our epistemic limitations, and identifies experimentation as a methodological approach for addressing these limitations.