We present a general model for the Continuous Prisoner's Dilemma and study the e!ect of errors. We "nd that cooperative strategies that can resist invasion by defectors are optimistic (make high initial o!ers), generous (always o!er more cooperation than the partner did in the previous round) and uncompromising (o!er full cooperation only if the partner does). A necessary condition for the emergence of cooperation in the continuous Prisoner's Dilemma with noise is b(1!p)'c, where b and c denote, respectively, the bene"t and cost of cooperation, while p is the error rate. This relation can be reformulated as an error threshold: cooperation can only emerge if the probability of making a mistake is below a critical value. We note, however, that cooperation in the continuous Prisoner's Dilemma with noise does not seem to be evolutionarily stable: while it is possible to "nd cooperative strategies that resist invasion by defectors, such cooperators are generally invaded by more cooperative strategies which eventually yield to defectors. Thus, the long-term evolution of the continuous Prisoner's Dilemma is either characterized by unending cycles or by stable polymorphisms of cooperators and defectors.