Journal of the History of Philosophy

Seventeenth-century advancements in physical science are often presented as overthrowing the Aristotelian tradition; perhaps Aristotle's emphasis on formal and final causes left little room for a physical theory grounded in material and efficient causes. In Aristotle's Science of Matter and Motion, Christopher Byrne argues that Aristotle is not to blame, as he indeed possessed a unified theory of matter and motion. In contrast to traditional interpretations, which place an undue explanatory burden on formal and final causes, Byrne argues that Aristotle's theory of the physical world is dependent on the features possessed by perceptible objects, qua perceptible, as well as non-teleological changes in matter.

Byrne's project develops in roughly three parts. First, in chapters 1–3, Byrne sets out the basic features of Aristotle's perceptible bodies that connect to motion and change. He argues that all perceptible bodies possess certain basic features that are required for an object to be a body, such as extension, divisibility, and mobility. Likewise, he argues that there are efficient causal principles that govern all interactions between physical objects, and there are hence unchanging patterns that govern both sublunary and celestial bodies. Byrne then argues that the material cause of a perceptible body is a substratum that persists and is physical. In cases of generation and corruption, the persisting substratum is essential to the formal cause, but the formal cause is not essential to the persisting substratum.

Next, in chapters 4–6, Byrne turns to an account of the material elements and the objects that they compose. First, Byrne shows that the matter underlying the mutual transformation of the elements is extended, corporeal matter; this is the case because generation and corruption requires a corporeal, persisting substratum. Second, Byrne explains the role of non-teleological necessity, which governs the interaction of tactile properties, and teleological necessity, which explains the natural motions of both sublunary and celestial bodies. Non-teleological necessity is prior to teleological necessity; accordingly, objects made from the elements, including homogeneous mixtures and even organisms, continue to be governed by both simple teleological and non-teleological necessity.

Finally, in chapters 7–9, Byrne turns to the role of formal and final causes within Aristotle's natural philosophy. Byrne argues that Aristotle's account of hypothetical necessity emphasizes the role of raw materials because formal causes are deficient: natural substances depend on formal causes but cannot be reduced to them because natural substances also possess non-accidental material natures. This means that perceptible objects, including organisms, may possess multiple natures and multiple layers of material causes; in turn, it is possible for a perceptible object to have multiple final causes.

Byrne's work does well to highlight the layers of complexity that are at work in Aristotle's account of the physical world. In contrast to the emphasis on formal causes found especially in the central books of the Metaphysics, Aristotle's works in natural philosophy permit a greater role for material and efficient causes within a complete explanation of the universe. Byrne's work provides one way to make sense of the layers of complexity in Aristotle's natural world, and in doing so, provides the start toward a plausible alternative to the top-down explanations characteristic of a traditional interpretation of Aristotle's natural world. [End Page 399]

Nonetheless, Byrne's emphasis on material and efficient causes may tend too far in the other direction. A traditional interpretation that requires a persisting substratum is already subject to difficulties regarding the unity of substance; specifically, it is subject to the objection that form is predicated of a substratum, and accordingly, all changes are accidental. Byrne retains the thesis, characteristic of traditional interpretations of Aristotle, that every instance of substantial change requires a substratum that persists or survives the change, but disagrees with the traditional interpretation because he takes it that such a substratum must be, at minimum, a body of some kind. Whereas a traditional interpretation can avoid difficulties by appealing to...