The author suggests that, although Donald Winnicott presented some important criticisms of Melanie Klein's work, at times he tried to advance his perspectives too definitively without adequately considering her own. Because of this, he failed to acknowledge sufficiently that he was offering a model of human nature and development that could be revised. The fact that his differences with Klein arose in the context of a complex relationship in which each played numerous roles for the other, especially in the context of their affiliation with the British Psychoanalytical Society, periodically made it difficult for him to present his ideas more carefully and in his more characteristically open manner.