Having reread David Estlund’s “Human Nature and the Limits (If Any) of Political Philosophy” (2011) – I had read it or similar material from Estlund years ago – I have some thoughts. Here is one. (For a variety of more shooting-from-the-hip points, of varying quality and level of present endorsement, see David Potts’ more-comprehensive critique Estlund’s article and specifically my comments there (Estlund’s Defense of Ideal Political Theory).)
*****
If agent X being unable to perform action (or carry out plan) A entails that it is not the case that X ought to perform A, why is this? This answer seems plausible: because this rules out A-ing as an option for X in her deliberation and decision-making. If this is right, then why suppose that only the ability/inability binary is relevant? Why not a cut-off in a relevant scalar quantity? Specifically: perhaps if it is unlikely-enough that X will pull off A (maybe or maybe not due to relevant deficits in X’s internal, psychological abilities), then A-ing is not an option for X — and so it is not the case that X ought to A.


