Journal of the History of Philosophy

Mariska Leunissen’s study focuses on teleology in Aristotle’s theory and practice of science. She proceeds from Aristotle’s general defense of teleology (chapter 1) to a more detailed discussion of how teleology works in the science of soul (chapter 2), of animal parts (chapter 4), and of cosmology (chapter 5). She also argues that Aristotle’s study of animal parts is a demonstrative science, in accordance with the model of the Posterior Analytics (chapter 3). In the brilliant final chapter 6, Leunissen argues for a new view of how final causes figure in scientific syllogisms: not as middle terms but as major terms that are the predicates of the conclusions of scientific demonstrations. The middle terms then pick out the causal features that bring about the final cause.

The book is of outstanding quality. The level of scholarship is very high, the solutions convincing and well argued, and the whole engaging. The highlights, I find, are Leunissen’s distinction between primary and secondary teleology and her discussion of the final cause in scientific syllogisms. The former enables her, among other things, to give a more independent role to material necessity than has previously been argued, while at the same time preserving its compatibility with teleology: not all material necessity is subordinated to teleology, but rather on its own it produces residue—selected and retained teleologically by nature—from which nature then produces functional animal parts. Such parts are not strictly necessary for the animal’s substantial being and are thus not conditionally necessary, but they have a function and serve the animal’s good. By means of the latter, Leunissen manages to integrate Aristotle’s examples of teleological explanation and inquiry into his theory of scientific demonstration. One of the general conclusions of the study is that biology, not mathematics, was Aristotle’s central model for science and that his scientific practice in fact follows his theory: the practice is more rigorous in searching for patterns of teleological explanation realized through material, efficient, and formal causes, and the theory more flexible than has often been supposed.

Leunissen’s discussion operates with a distinction between cause and explanation, briefly commented on at the beginning of chapter 1 (10, n. 2). In that context, correctly taking Aristotle as a realist concerning both cause and explanation, Leunissen contends that the answers given to “why” questions will be explanatory and hence productive of scientific knowledge “if they pick out real causes.” She argues that whereas teleology for Aristotle enjoys explanatory priority, other cause-types are causally prior. One might then ask whether such a distinction between explanatory and causal priority coincides with Aristotle’s distinction between what is prior to us and prior in nature. Leunissen’s conclusion offers a closer account of cause and explanation and a partially affirmative answer. The view that final causes occur in the conclusions of demonstrations is coupled with their being “closer to us” (211), that is, better known to us in Aristotle’s distinction. Therefore, final causes provide us with starting points for the discovery of causally prior factors, that is, the middle terms of scientific demonstrations that are further away from us and hence, supposedly, better known in nature. However, ends and functions are also identified as being “prior in nature,” whereas formal, efficient, and material causes are prior in generation (214). This indicates that the correspondence with Aristotle’s distinction is not quite complete. [End Page 611]

The discussion also invites some speculation about such teleological principles as “nature does nothing in vain.” Leunissen argues convincingly (especially in section 4.2) that Aristotle uses them as heuristic tools for searching for the causally primary factors, but that they do not occur as premises of demonstrations—being formally unsuited for that as well (not being of the form ‘A of B’). However, Aristotle also supposes that such principles produce adequate results in the search for causes, and Leunissen grants that they are “generalizations over . . . the observed outcomes...