  In 1980 Steven Smale introduced a class of strategies for the Iterated
Prisoner's Dilemma which used as data the running average of the previous
payoff pairs. This approach is quite different from the Markov chain approach,
common before and since, which used as data the outcome of the just previous
play, the memory-one strategies. Our purpose here is to compare these two
approaches focusing upon good strategies which, when used by a player, assure
that the only way an opponent can obtain at least the cooperative payoff is to
behave so that both players receive the cooperative payoff. In addition, we
prove a version for the Smale approach of the so-called Folk Theorem concerning
the existence of Nash equilibria in repeated play. We also consider the
dynamics when certain simple Smale strategies are played against one another.
