Aristotle is a pluralist in more ways than one. He recognizes, for example, many kinds of goods, beings, and varieties of knowledge. A focus of much recent Aristotelian scholarship has been to show just how extensive this pluralism and its implications are. Although Aristotle aims to show how these pluralities hang together, he rarely explains how. This work is left to the exegete.
So too, in regard to aitiai (causes and, insofar as they are knowable as causes, explanations). Stein’s book is devoted to Aristotle’s pluralism in regard to aitiai. It is a commonplace that Aristotle is in fact a causal and explanatory pluralist—his account of the four causes is among the most famous aspects of his philosophy. The innovations of Stein’s book lie in how it uncovers the philosophical motivations and implications of this pluralism. On Stein’s account, it is reflection on the nature of causation as such, not linguistic analysis of “why?” questions or ontological analysis of composite substances, which leads him to distinguish four kinds of causation. Stein’s Aristotle aims to avoid the fundamental error of his predecessors: explanatory reductionism (to be distinguished from ontological reductionism), according to which there is only one basic kind of cause at work in the world. There is more than one kind of causal relation, but all must be intelligible and recognizably applicable to changes and events recognized as real aspects of the world.
The fundamental metaphysical problem concerning causation concerns the nature of the link between cause and effect. If the two are discrete from one another, it would seem that any relation between the two is contingent. But if the effect is somehow contained in the cause, the two are not discrete. There is also a basic epistemological question concerning this causal link. A state of affairs of a certain kind is perceived, and, independently, a subsequent state of affairs, but we do not perceive a causal link between the two. So how do we know that there is such a causal link, and how can that link itself be an object of knowledge?
Aristotle first works through an account of causality in the Posterior Analytics. His primary concerns there are those explanations that take the form of demonstrations, of which the explanantia are predications, grounded in definitions. These explanantia are immediately intelligible principles, and the explanandum is a necessary and eternal predication which follows from them as a matter of logical necessity. Although the fundamentals of Aristotle’s account of causality and demonstration are to be found in his account of such demonstrations, it is not the focus of Stein’s book. This is, I think, in part because the core problems with which it is concerned do not arise for demonstrations as discussed in the Posterior Analytics, as they are often interpreted. For if we take immediate premises to be definitional, the major term is included in the definition of the middle term, and the middle term is included in the definition of the minor term.[1] In such a case the explanandum, the major term, is not discrete from the cause, the minor term, and the fundamental problems concerning causality do not arise. So Stein’s primary concern is Aristotle’s development of this account, in Physics and subsequent works, according to which the explanantia are not predications but things that come to be and the changes they undergo. In such cases the nature of the bond between cause and effect is more problematic. Stein calls the basic relation between cause and explanandum “the causal profile”. He finds in Aristotle two basic kinds of causal profile. In both cases, as in the Posterior Analytics, the fundamental causes found in these causal profiles are features intrinsic to the basic subjects, expressed in definitions. In “origin-dominant” causal profiles the key causal link is grounded in what is present prior to the change: these include instances of efficient and material causation. In “end-dominant” causal profiles the key causal link is rooted in the result of a change; these include instances of final causation and, in the case of the development and activities of natural substances, instances of formal causation.
In the Posterior Analytics, the basic causes are predications that are intrinsic to their subject, those that, in Aristotle’s terms, hold of their subjects kath’ hauta. On the basis of these predications one can deduce the predication that is the explanandum. In the Physics and subsequent works, the basic causes (in both origin-dominant and end-dominant causal profiles) are not predications but causal powers (dunameis), again intrinsic to the subjects in question. This allows Aristotle to explain particular changes. The explanatory scheme of the Posterior Analytics would presumably allow for explaining predications, for example, why all instances of fire always have a certain feature; but in order to explain changes, such as when something in contact with fire is heated by it, one must appeal not to basic premises but to basic powers, for example, the active power of the fire and the passive power of what is heated.
Stein shows how, by positing such powers as intrinsic causes, Aristotle bridges the ontological gap between the agent and patient. The fire and the object it heats, say, a rock, are discrete objects, and as such the active power intrinsic to the former is independent of the passive intrinsic power of the latter. But when they come to stand in the appropriate relation to one another, there is a single event, which could be described either as the first heating the second, or the second being heated by the first. Although the fire and the rock are discrete, the fire and the change undergone by the rock are not. By identifying the powers involved, the change is rendered intelligible. In more complex processes, for example, that by which a builder builds a house, these immediate connections are linked, and this makes possible the action of extrinsic causes (for example, the power of a flame, under the direction of a baker, to bake a loaf of bread; heating is intrinsic to fire, but baking is not). The chain of causal links constitutes a kind of mechanism, for which reason Stein argues that Aristotle’s account of causality is in this regard much like that of today’s “neo-mechanists”. (Note that this is not to be confused with the sort of mechanism that reduces all events to the level of basic material interactions; the idea is rather that all events are to be understood as resultant from component causal bonds.)
Stein stresses that Aristotle denies that all of the relevant causal powers are to be found at the level of elemental interactions. Complex homoiomerous stuffs have active and passive causal powers of their own, as do the living things that they constitute. Beyond that, Aristotle recognizes the active power of the builder to build and the passive power of the bricks to be built. These powers are as basic as those of any material interaction, such as the hammer driving the nail. Causal links and the mechanisms that they constitute are at play at multiple levels, and the higher levels are not to be reduced to the lower.
Stein concludes by turning to epistemological problems posed by causal relations, familiar to us from Hume’s challenge concerning our knowledge of the bond between cause and effect. We perceive one event, and then perceive another, but we do not perceive a causal nexus between the two. After observing enough similar events, one is entitled to say that events of the first kind cause events of a second, but, for Hume, such a claim has no ontological implications.
Philosophy of science has by and large moved beyond such uncompromising empiricism and has accepted scientific realism of one sort or another. Entities are posited as the basis for the causal connections that are responsible for these regularities. If one rejects ontological reductionism, science is to be understood as concerned with the middle-sized objects familiar from day-to-day life, which make up what Sellars called “the Manifest Image”. Sellars took Aristotle to be the philosopher of the Manifest Image,[2] and Stein explicitly agrees. Middle-sized objects that are natural substances are the primary entities posited by the scientific explanations that Aristotle takes to be employed in the natural sciences. But does this not leave Aristotle open to the sorts of epistemological challenges introduced by Hume? This would be so only if Aristotle takes the empirical basis of scientific accounts to be restricted to common and proper sensibles (color, shape and the like), excluding not only natural substances but the causal connections between the events in which they are implicated. But Aristotle’s notion of perception is much more expansive than that. He thinks that we have direct epistemological access to the things that Aristotle calls “more knowable to us”—the basic objects in the Manifest Image—and are able to grasp the causal powers that belong to them kath’ hauta. “[A]t least some causality is such that it can be grasped with our more basic cognitive powers of judgment . . . without going beyond the conceptual resources available to ordinary perceptual judgment” (17). Of course, not all causal mechanisms accounted for by science are immediately observed. Some of the subordinate causal profiles (especially in the case of final causation), are inferred and Aristotle is well aware that some of these inferences are provisional. But, Stein argues, Aristotle thinks basic causal connections, whether at the elemental level (fire heating a rock) or at the higher levels embedded in human sociality (a builder exercising a craft) are as epistemologically accessible through perception and as certain as anything is.
Stein’s focus is Aristotle’s account of the kind of causal explanation employed in the natural sciences, especially insofar as they appeal to sequences of efficient causation, which Stein understands as akin to mechanisms. He takes Aristotle’s key insight to have been that explanatorily basic entities are in a number of relationships with one another and that these linkages are largely nonlinear. Stein contrasts the sorts of explanation that explicate these mechanisms with the canonical variety of demonstration discussed in the first book of the Posterior Analytics, which he takes to be “logically and metaphysically simpler” (69). I have elsewhere argued that within the Posterior Analytics Aristotle understands even demonstrations that focus on formal or essential causation, as those found in mathematics, to explicate complex relations in which basic entities stand in respect to one another.[3] To be sure, these are not mechanisms, as this term is reserved for complex structures that make efficient causation possible. I nonetheless take Stein’s work, in regard to efficient causation, as a welcome complement to this interpretation of the structure of the canonical demonstrations discussed in the Posterior Analytics.
Throughout, Stein shows how Aristotle’s account of causation and explanation is at work in a number of the physical treatises, and he concludes his book with a special focus on Aristotle’s account of blood, in Parts of Animals.
It is not often that we see a work approaching Aristotle’s core writings with a new set of questions inspired by recent developments in philosophy, rich with insights into the questions Aristotle is asking and the answers he develops. Stein’s book is such a work, and it deserves close study by all with interests in Aristotle’s metaphysics, epistemology, and philosophy of science.
Notes
[1] As I note at the conclusion of this review, I do not in fact take most Aristotelian demonstrations to take this form.
[2] W. Sellars, “The Structure of Knowledge”, in Hector-Neri Castañeda (ed.), Action, Knowledge and Reality: Studies in Honor of Wilfrid Sellars (Indianapolis: Bobbs Merrill, 1975), 303.
[3] O. Goldin, “Atoms, Complexes, and Demonstration: Posterior Analytics 96b15-25”, Studies in History and Philosophy of Science 35 (2004), 707-27.