 Richard Samuels (1998; 2002; 2004; 2007) has developed a version of Cowie’s mystery hypothesis called psychological primitivism. On this view, that a belief or behavior is ‘innate’ means that it serves as an explanatory primitive for psychological science. An explanatory primitive is a concept that is deployed by a discipline to explain certain phenomena, but which cannot in principle be explained by that discipline. Samuels maintains that there is a sharp explanatory boundary between psychology and other fields. A necessary condition for any psychological explanation, he claims, is that it apply to the whole organism and not to a specific (sub-personal) component (Samuels 1998). This condition excludes many explanations couched in neurobiological terms, because they apply to sub-personal components and not to the organism as a whole. However, there are other predicates that apply to the whole organism and yet do not qualify as psychological (e.g being a carnivore). So, the personal/sub-personal distinction is not sufficient for marking the boundary that Samuels wants to draw. As a result it is not entirely clear how to draw the line between psychological and non-psychological phenomena. Samuels examples of psychological explanations feature processes such as conditioning, perception, and inference; whereas neurological and hormonal explanations purportedly fall outside psychology (Samuels 1998; 2002; 2004). Some authors criticize Samuels’ primitivism on the grounds that this sharp distinction between psychology and other sciences does not exist (Gross and Rey 2012; Linquist 2018). For example, psychological explanations of depression and anxiety cite both intentional states and sub-personal processes as components of the same mechanism. The issue of how psychological explanations are related to biological explanations is one of the most pressing questions in the philosophy of cognitive science and has recently been explored in the context of debates over mechanistic explanation (see Gaj 2016; Milkowski, et al. 2019 for reviews).