The term “mechanism” emerged in the seventeenth century and derived from Greek and Latin terms for “machine” (Dijksterhuis 1961). Descartes understood mechanics as the basic building block of the physical world; in Le Monde, he proposed to explain diverse phenomena in the natural world (such as planetary motion, the tides, the motion of the blood, and the properties of light) in terms of the conservation of inertial motion through contact action (see the entry on  René Descartes). Subsequently, the  idea of mechanism has been transformed many times to reflect an evolving understanding of the basic causal forces in the world (besides conserved motion): e.g., attraction and repulsion (du Bois Reymond), conservation of energy (Helmholtz), gravitational attraction (Newton) (Boas 1952; Westfall 1971; see also entries on  Hermann von Helmholtz and  Isaac Newton). The concept of mechanism has had an almost separate evolution in the history of the life sciences (Allen 2005; Des Chene 2001, 2005; Nicholson 2012), at times eschewing the metaphysical austerity embraced by Descartes and many early mechanists.