PHYSICS The Stoics say that every cause is a body that becomes for another body a cause of something non-bodily For instance a scalpel, which is a body, becomes for the Xesh, another body, a cause of the non-bodily predicate being cut Again a Wre, which is a body, becomes for the wood, another body, a cause of the non-bodily predicate being burnt (M 211) While A and B are both material entities, the Stoics used the term ‘matter’ specially to refer to B, the passive element in causation (Seneca, Ep 65 LS 55e) So in Stoic causation we have a triad of cause, matter, and eVect The Stoics introduced the notions of joint causes (sunaitia) and auxiliary causes (sunerga) Two oxen are joint causes of the movement of the plough if neither of them can pull it alone; I am an auxiliary cause if I help you lift a load which you can, at a pinch, manage by yourself (LS 55i) The recognition of joint and auxiliary causes was important, because it shows that it can often be misleading to speak of the cause of a particular state or event Causes form not a chain, but a network For the Stoics it is not only changes and beginnings of existence that need causes: there are also sustaining causes (aitiai synektikai) that bring it about that things continue in existence Bodies of all kinds, for instance, are held together by an active and tenuous Xuid called pneuma, literally ‘breath’, which is responsible for the cohesion of the universe Living bodies are kept alive by the soul, which is their sustaining cause It is characteristic of such causes that if they cease to operate, their eVects cease to obtain Zeno, indeed, stated this characteristic as a feature of all causes (LS 55a); but other Stoics seem to have allowed another category of antecedent (prokatarktikai) causes, whose eVect remained after they had been removed (LS 55i) It seems obvious enough that a house may remain in existence long after the builder has ceased working What Zeno seems to have had in mind were sustaining causes that sustained something other than existence or life: it is prudence, for instance, that brings it about that a man is prudent, and he is prudent only for so long as his prudence lasts Prudence, it must be remembered, was for Stoic materialists a physical ingredient of a person (LS 55a) The way in which the existence of antecedent causes is to be reconciled with Zeno’s theory of sustaining causes seems to have been this: an antecedent cause brings it about that an object possesses an internal feature that is itself a sustaining cause simultaneous with the eVect to be explained This, certainly, was the form the theory took when it was employed to 193