Neutrality between Tit for tat and unconditional cooperation ($e(T,T)=e(C,T)=e(T,C)=e(C,C)=R$)

Under cooperative initial memories, matches involving only Tit for tat and always cooperate contain only cooperation, so all four payoffs equal $R$. The two-condition criterion for evolutionary stability has both differences zero. Thus Tit for tat is not an evolutionarily stable strategy against a strategy space containing unconditional cooperation, even if it is a Nash equilibrium. This counterexample is valid for finite horizons and discounting as well as infinite averages.