Medieval philosophy a new history of western philosophy volume 2 ( PDFDrive ) 228

METAPHYSICS Ockham’s principal philosophical argument against the reality of quantity is derived from the phenomena of expansion and contraction, rarefaction and condensation If a piece of metal is heated and expands from being 80 cm long to being 90 cm long, then, on the theory he is attacking, it changes from possessing an accident of 80-cm-longhood to possessing another accident of 90-cm-longhood Ockham argues that it is diYcult to give a convincing account of where the second accident has come from, and what has become of the Wrst accident Moreover, if the change is a continuous one, so that the metal has expanded through lengths of 81 cm to 82 cm and so on, then there will be an inWnite number of Xeeting accidents coming into and going out of existence This, Ockham claims, strains our credulity The local motion by which one part moves away from another part is quite suYcient to explain such phenomena Accordingly, real accidents of quantity are quite superXuous, and should be eliminated from philosophical consideration One might think that similar considerations might be used to show that qualities, too, were not real accidents Aristotle had listed four kinds of quality: (a) dispositions like virtue and health, (b) inborn capacities, (c) sensory properties like colour, taste, heat, (d) shapes Ockham was willing to eliminate some of the qualities in the Wrst class, like health and beauty, and he applied his razor very explicitly to qualities in the fourth class When a proposition is true of reality, if one thing is suYcient to make it true, it is superXuous to posit two But propositions like ‘this substance is square’ ‘this substance is round’ are true of reality; and a substance disposed in such and such a way is quite suYcient for its truth If the parts of a substance are laid out along straight lines and are not moved locally and not grow or shrink, then it is contradictory that it should be Wrst square and then round So squareness and roundness add nothing to a substance and its parts (OTh 707) But he maintained that other qualities, notably colour, were diVerent It is impossible for something to pass from one contradictory to another without gaining or losing something real, in cases where this is not accounted for by the passage of time or by change of place But a man is Wrst non-white, and afterwards white, and this change is not accounted for by change of place or the passage of time Therefore, the whiteness is really distinct from the man (OTh 706) One might think, however, that a gradual change of colour was quite parallel to a gradual change of size: the implausibility of an inWnite series of 209