  Many readers of Nishida have attempted to delineate stages in the development of his philosophy (Elberfeld 1999, 71ff.); others have rejected a division into discrete stages (Heisig 2001, 104). As a heuristic approach to a summary of his thought, we may broadly distinguish three stages. The first is defined by an overwhelming conviction that concrete reality is at base unitary and can be articulated from the standpoint of consciousness. We have seen that Nishida successively names its most basic form  “pure experience,” “self-awareness,” and “absolute free will.” Each of these exemplifies the fundamental reality from which all else becomes manifest through a process of differentiation. In An Inquiry Into the Good (1911), pure experience describes the primal undifferentiated form that subsequently dirempts into differentiated forms: experiencing subject and experienced objects, intellectual intuition and reflective thought, objectified nature and objectifying spirit—all on their way to a higher unity.  Intuition and Reflection in Self-Awareness (1917) shifts that idealistic description to epistemological questions. It explicates self-awareness as the form in which reflection and immediate experience or intuition are unified, that is, the form that reflects itself within itself and gives rise not only to differentiating judgments but to differently experienced systems such as spirit and matter and to “worlds” such as art and religion.  Eventually Nishida proposes that the most basic form of self-awareness is not a kind of knowing at all, but a willing or “absolute free will” evident in valuing and creating. He develops this proposal in Problems of Consciousness (1920) and Art and Morality (1923).  Nishida later said his first attempts, formulated from the standpoint of consciousness, invited the charges of psychologism (Nishida 1990, xxxi), and mysticism (Nishida 1987, xxiii), and so he abandoned the language of pure experience and absolute will. It is clear, however, that his initial convictions persisted a good deal longer: the most concrete form of reality is undifferentiated, and consciousness as the manifestation of reality is inseparable from it.