 To see all of this a little better, it will help to return to the important distinction made by Steven Savitt discussed in Section 1 between ontologically conservative (or retentive) theory change on the one hand, and ontologically radical (or eliminative) theory change on the other hand. Ontologically conservative theory change occurs when the entities and posits of the replaced theory are relocated, often with some degree of revision, in the replacing theory. For example, as our theory of light was gradually replaced by our understanding of electro-magnetic radiation, our conception of light was dramatically transformed as we recognized ways in which our old conception was mistaken or incomplete. Nevertheless, at no point did we come to say that there is really no such thing as light. Rather, light was eventually identified with a form of electro-magnetic radiation.