 Aristotle  is the foundation for both philosophical themes pertaining to reductionism. He addressed the relationship between domains of scientific knowledge in his concepts of superordinate and subordinate sciences (Posterior Analytics I). Each science has a distinctive subject genus, first principles, and set of predicates that are commensurable with the subject genus (McKirahan 1978, 1992, ch. 4–5). Though the relations among sciences are systematic, they are not necessarily reductive because there is no most fundamental science. These connections are relevant to relations between parts and wholes because Aristotle utilized his science of elements and their potentials (e.g., as seen in On Generation and Corruption and Meteorology) to inform his description and analysis of organism components in the History of Animals and Parts of Animals. He treated three compositional “levels”: elements and their potentials; uniform parts such as blood and bone; and, non-uniform parts that include multiple uniform parts, such as the face or hands. The primary domain here is physiology/functional anatomy but development/reproduction is always in view and addressed directly in the Generation of Animals. Claims about “potentials” are buttressed by an account of their contributions to material properties composing uniform parts (Meteorology IV; see Lennox 2001, ch. 8; Popa 2005). Complex dispositions (e.g., the fleshy, sinuous elasticity of the esophagus) are postulated from these material substrates that have relevance to, but do not determine the nature of, these organismal parts because functional strictures ultimately govern them (the fleshy, sinuous elasticity of the esophagus is for the sake of repeated dilation during food ingestion).