 In unificationist accounts of explanation developed by philosophers, scientific explanation is a matter of providing a unified account of a range of different  phenomena.[9]  This idea is unquestionably intuitively appealing. Successful unification may exhibit connections or relationships between phenomena previously thought to be unrelated and this seems to be something that we expect good explanations to do. Moreover, theory unification has clearly played an important role in science. Paradigmatic examples include Newton’s unification of terrestrial and celestial theories of motion and Maxwell’s unification of electricity and magnetism. The key question, however, is whether (and which) intuitive notions of unification can be made more precise in a way that allows us to recover the features that we think that good explanations should possess.