Ever since Bruner’s, attempt in 1966 to refute Piaget’s insistence that it is the prior recognition of reversibility (i.e., the reversible operations of inversion and compensation) which entails the development of conservation, and not vice versa, many other researchers have sought to explore this issue with a variety of logical arguments and research paradigms. Unfortunately, however, many of these individuals have not accurately represented, and so tested, Piaget’s actual theory. This paper is an attempt to clarify Piaget’s distinctions and meanings, and then, considering these clarifications, to review the state of our knowledge on this issue. It is concluded that reasonable evidence does now exist suggesting that conservation by identity may precede and induce the emergence of conservation by inversion and compensation. Implications are discussed and new lines of research are suggested.