The authors explore Heinz Kohut's ideas of self, including its nuclear and virtual forms, in the critical period from the late 1960s to about 1975. Kohut's creative process, it is argued, has not been fully appreciated. The authors establish the baseline of Kohut's ideas about the self in his first book, The Analysis of the Self in 1971. His ideas then evolved significantly in the next few years, as he came to define the self as the center of psychological experience and then to consider what he came to call the nuclear self and the virtual self as extensions of his core ideas about the self-selfobject system. The authors trace the specific sequence of conceptual steps that Kohut took in his reexamination of what he meant by self. Kohut's thinking in this area proceeded unevenly and not always chronologically. His pathbreaking work in the early 1970s on fragmentation, on the cohesion and continuity of the self, and on the mutable nature of the nuclear self and the virtual self represents a seminal development in the understanding of these psychoanalytic concepts.