PHYSICS of matter Therefore the ultimate subject is of itself neither of any kind or any size nor anything else (Metaph F 1029a21–5) An entity that is not of any kind or any size or any shape, and of which nothing at all can be said, appears to be highly mysterious But that is not what Aristotle is inviting us to accept His ultimate matter (he sometimes calls it prime matter) is not in and of itself of any kind It is not in and of itself any particular size, because it can grow or shrink; it is not in and of itself water, and it is not in and of itself steam, because it is each of these in turn This does not mean that there is any time at which it is not of any size, or any time in which it is neither water nor steam nor anything else How then is a chunk of matter to be identiWed? Well, in everyday life we are familiar with the idea that one and the same parcel of stuV may be Wrst one kind of thing, and then another kind of thing A bottle containing a pint of cream may be found, after shaking, to contain not cream but butter The stuV that comes out of the bottle is the same stuV as the stuV that went into the bottle: nothing has been added to it and nothing has been taken from it But what comes out is diVerent in kind from what goes in It is from cases such as this that the Aristotelian notion of matter is derived The Stoics on Causality The Stoic account of causes is both simpler and more complex than the Aristotelian one It is simpler in that the Stoics not count the material, formal, and Wnal causes as causes properly so called, and they mock Aristotle’s followers’ ‘crowd of causes’ (Seneca, Ep 65 4) Their treatment of eYcient causes, however, is more complex, in that they adopt a canonical form for the description of causation, and they oVer a rich classiWcation of diVerent kinds of cause Most importantly, unlike Aristotle, they oVer a law of universal causation, which needs to be spelt out and defended The Stoics’ standard analysis of causation was of the following form: A brings it about that B is F A, the cause, must be a body, and so must B; but the eVect, B’s being F, is not a body but an abstract entity, a lekton This is explained by Sextus: 192