Animal Locomotion in Aristotle: Self-Motion and the Tripartite Scheme

In De Anima III 10, Aristotle proposes a notable tripartite scheme of animal self-locomotion. Though many note that the proximate source of the scheme is in Physics VIII 5 (Ferro 2022; Laks 2020; Polansky 2007; Rapp 2020a; Shields 2016), it is nevertheless surprising that Aristotle chooses a scheme of general locomotion from Physics, rather than choosing some of his specific work there on animal self-motion. Further, the two tripartite schemes don’t line up very precisely. I defend a novel view on which the tripartite schemes are understood as non-fundamental, since their authority rests on a more basic Separability Thesis advanced in Physics VIII, which states that every self-mover has minimally two parts: an unmoved mover and a moved part. While the importance of the Separability Thesis has been frequently noted in the literature (e.g., Morison 2004; Waterlow 1982), its relationship to the tripartite schemes has not been explored. I argue that once the fundamentality of the Separability Thesis is recognized, the tripartite schemes can be understood as two different applications of it and Aristotle’s theory of self-motion from Physics is therefore present, in a veiled way, even in De Anima III 10. Further and finally, the argument provides resources for offering a novel response to worries about the unity of self-movers.