 In more recent work, Stewart and Plotkin (2013) present evidence that supports a qualifiedly affirmative answer to the open question. Their work borrows from a detailed mathematical investigation of the infinite IPD by Ethan Akin. Akin, 2013) focuses on strategies that satisfy exactly the conditions we might want for a morally appropriate “solution” to the 2IPD: (1) use by both players ensures the cooperative payoff, (2) use by both players constitutes a nash equilibrium, i.e., a strategy-pair giving each player a payoff that he cannnot improve upon by deviating from it unilaterally and (3)use by both players prevents exploitation by either—any change in strategy by either player that reduces the payoff of his opponent will also reduce his own. Akin labels such strategies “good” and derives a remarkably simple characterization of them. A strategy \(\bS(p_1,p_2,p_3,p_4)\) is good if and only if it meets the following conditions: