Abstract. In the context of the relationship between signs and concepts, this paper tackles some of the ongoing controversies over conceptual development and change -including the claim by some that concepts are not open to revision at alltaking the position that concepts pull apart from language and that concepts can be discussed on at least four levels: that of individual agent, community, society, and language. More controversially, it claims that concepts are not just inherently open to revision but that they, and the frameworks of which they form part, are in a state of continuous, if generally incremental, change: a position that derives directly from the enactive tradition in philosophy. Concepts, to be effective as concepts, must strike a careful balance between being stable enough to apply across suitably many contexts and flexible enough to adapt to each new context. The paper's contribution is a comparison and contrast of conceptual development and change on four time scales: that of the day-to-day life of an individual conceptual agent, the day-to-day life of society, the lifetime of an individual agent, and the lifetime of society and the human species itself. It concludes that the relationship between concepts and experience (individual or collective) is one of circular and not linear causality.