 According to Richard Samuels’ proposal, human nature should be understood as the empirically discoverable proximal mechanisms responsible for psychological development and for the manifestation of psychological capacities. These will include physiological mechanisms, such as the development of the neural tube, as well as environmentally scaffolded learning procedures; they will also include the various modular systems distinguished by cognitive science, such as visual processing and memory systems (Samuels 2012: 22ff.). Like mere list conceptions (cf.  §3.2),  such an account has a precedent in Hume, for whom human nature also includes causal “principles” that structure operations of the human mind (1739–40, Intro.), for example, the mechanisms of sympathy (III,iii,1; II,ii,6). Hume, however, thought of the relevant causal principles as intrinsic.