The recent surge of interest in e-science presents an opportune moment to re-examine the fundamental idea of “data”. This paper explores this topic by reporting on the different ways in which the idea of data is handled across many disciplines. From the accounts various disciplines themselves provide, these ways can be portrayed as the pursuit of three broad policies. The first policy is one of Indifference, which assumes the coherence of the data-concept, so that there is no need to explicate it further. The second policy is Purification, which identifies the essential characteristics of data according to the conventions of a particular discipline, with other modes systematically suppressed. The third policy allows for the Differentiation that is evident in the manifestations of data in various disciplines that utilise information systems. Greater appreciation among information professionals of the alternative approaches to data hopefully will enhance policy formulation and systems design.