Fortunately, there is heat; and Freudenthal is keen to promote it as an overlooked central factor in Aristotle’s theory of material substance. He begins in agreement with the many scholars who argue that Aristotle’s theory of the four elements underdetermines the plain fact that there are organic substances which exhibit both synchronic and diachronic unity. He goes further than most, however, by arguing that left unaugmented Aristotle’s account of the four basic elements would positively preclude the existence of these forms of unity. For Aristotle embraces the Presocratic picture of the four elements as engaged in “endemic strife”, so constituted that their natural propensities lead them to separate and dissolve rather than to unite and synthesize. Thus, for example, each of the four elements has a natural direction, which ought to result in fire and air ever moving upward and away from earth and water, which will move downward if unimpeded. Hence, as Aristotle himself recognizes, some agent force is required to hold the four elements together when they are mixed.