This paper explores the development of a particular talmudic halakhic theme—the restitution of lost property—through the philosophical prism of Hilary Putnam's distinction between concepts and conceptions. This distinction holds that one can affirm a set of concepts without commitment to the underlying conceptions from which they are drawn. The focus here is upon substantial discrepancies between tannaitic and amoraic authorities in the presentation of the halakhot of restitution of lost property. These discrepancies testify to a significant change in the underlying conceptual framework of tannaitic and amoraic halakhic thinking on this topic.