In this paper I argue that non-reductive physicalism (NRP) continues to rely on the ontological aspect of the layer cake model of the world (LCM). NRP is a post-unity account of the relationship between phenomena in the world in the sense that it has been developed in response to the perceived failure of the unity of science thesis. The LCM constitutes a framework for the organisation of phenomena in the world. It
articulates the idea that phenomena in the world are organised into levels. Specifically, that phenomena are layered into distinct, hierarchical levels of organisation. Historically, the unity of science thesis and the LCM have been intertwined; the LCM being the framework within which a unity of science might be possible. My argument
will demonstrate that, despite a move away from unity of science positions, the LCM persists in post-unity accounts. In order to argue for this thesis, I present a close analysis of Oppenheim & Putnam’s classic presentation of the LCM; picking out the
principle of hierarchic compositionality which, I argue, captures the ontological aspect of the LCM. I then demonstrate how NRP continues to rely upon the principle and, as a result, continues to support the ontological aspect of the LCM. This result is significant. It shows that whilst the rejection of the reductionist aspect of the thesis has served as the basis for post-unity positions these positions do not engage directly with the framework within which reduction might be facilitated – the LCM. Furthermore, it demonstrates that pluralist or disunity accounts of the relationship between phenomena in the world will also have to engage directly with the framework of the LCM in order to avoid being merely anti-reductionist.