‘To understand is to invent’ (Piaget, 1968). This paper examines the attempt of Les Dale, the Assistant Director of the Australian Science Education Project, to apply Piagetian theory to describing a theory of instruction for the Project. The historiographical method consists in examining and comparing instances of curriculum invention in science education in Australia starting with contemporary and retrospective accounts of the key figures (Fawns 1988a). This paper is a case record (Stenhouse, 1978) which synthesises public and personal material in the files collected by the author. It has been subjected to review by Dale and others including those to whom it was presented at A.S.E.R.A. It accompanies an earlier paper (Fawns, 1989) which assessed the social context of the Debate at the Guidelines Conference 20 years on.