 In each area of inquiry Philolaus appears to proceed by identifying the minimum number of archai, “beginnings” or “starting points,” necessary to explain the phenomena in that area (Huffman 1993, 78–92). In the case of the cosmos as a whole, as we have just seen in Fr. 6, Philolaus argues that three starting points must be assumed, limiters, unlimiteds, and harmony, as a third element to hold these two unlike elements together. In the case of disease, Philolaus identifies three archai, bile, blood and phlegm (see 6.2 below). In the case of living creatures, the brain is the starting point to which we must appeal to explain human beings, the heart as the seat of sensation is the crucial factor in explaining animals, the navel as the seat of rooting (the umbilical cord is regarded as a root) is the distinctive starting point of plants, and finally the genitals are a factor common to all animate beings in contrast to the inanimate world (Fr. 13, see 5.1). This approach to explanation seems to have been developed under the influence of contemporary mathematicians and medical writers. Graham argues that in his use of archai to mean something like “principles” Philolaus achieves “ a level of abstraction that surpasses ... probably all of his predecessors” and takes an important step towards Aristotle’s conception of archai as starting points of being or explanation (Graham 2014: 62). 