  Nagel distinguishes two types of reductions on the basis of whether or not the vocabulary of the reduced theory is a subset of the reducing theory. If it is—that is, if the reduced theory \(T'\) contains no descriptive terms not contained in the reducing theory \(T\), and the terms of \(T'\) are understood to have approximately the same meanings that they have in \(T\), then Nagel calls the reduction of \(T'\) by \(T\) “homogeneous.” In this case, while the reduction may very well be enlightening in various respects, and is part of the “normal development of a science,” most people believe that there is nothing terribly special or interesting from a philosophical point of view going on here. (Nagel 1961, 339.)