Research claiming a measurable link exists between HR practices and organizational performance is recognised to be under-theorised. Appropriate theory is unlikely to emerge and develop by researchers doing more, and/or better, empirical work. The current unwillingness to reflect on meta-theory, coupled with the preoccupation with empirical techniques, does nothing to encourage the development of theory. Our meta-theoretical reflection, especially upon the nature of theory, permits a working definition of theory and illuminates the further problem that research lacks explanatory power. Under-theorisation and lack of explanatory power manifest themselves in the Black Box problem and the problem of measurement without theory. We consider the work of three sets of writers who have explicitly attempted to identify theories that might provide the requisite theoretical insights.