= Neutrality between Tit for tat and unconditional cooperation
{title2=$e(T,T)=e(C,T)=e(T,C)=e(C,C)=R$}
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.
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