Nature Does Nothing in Vain: Reexamining Aquinas’s Fifth Way Joel Johnson AT THE BEGINNING of his Summa theologiae, Thomas Aquinas famously presents his Five Ways to demonstrate the existence of God. In each of the Five Ways, he draws attention to some general feature of the world and argues that this feature can only be explained by a divine being. In his Fifth Way, Aquinas takes as his starting point the observation that beings that lack cognition act for the sake of ends, and his explanation for this phenomenon is a divine intelligence who directs such beings to their ends. However, as is the case with each of the Five Ways, the proper interpretation of the Fifth Way is a matter of dispute. Commentators disagree about both the precise nature of the end-directed activity in question and the exact manner in which an intelligent being explains it. In this article, I consider the three dominant interpretations of the Fifth Way found in recent literature and argue that, while each of these interpretations accurately captures important elements of Aquinas’s understanding of final causality, each interpretation also faces serious textual or philosophical difficulties. I then propose a fourth interpretation of the Fifth Way that circumvents the problems that undermine these other interpretations. The fact that the text of the Fifth Way is interpreted in several incompatible ways is in large part due to its brevity. Aquinas states the entirety of the argument as follows: [End Page 43] The fifth way is taken from the governance of things: We see that some things lacking cognition, namely, natural bodies, act for an end. This is apparent from the fact that they always or very frequently act in the same way so that they attain what is best, and from this it is clear that it is not by chance, but intentionally, that they attain the end. But things lacking cognition tend toward an end only if they are directed by something that has cognition and intelligence, in the same way that an arrow is directed by an archer. Therefore, there is something with intelligence by which all natural things are ordered toward an end—and this we call a God.1 At its core, the argument is a simple modus ponens: 1. Things that lack cognition, namely, natural bodies, act for an end. 2. If natural bodies act for an end, then they must be directed to the end by something with cognition and intelligence. 3. Therefore, there exists something with cognition and intelligence that directs natural bodies to an end, and this we call a God. Although this basic characterization of the argument is accepted by each of the rival interpretations considered in this paper, disagreements arise in their attempts to clarify both the meaning of and the justification for both premises. However, before turning to these rival interpretations, three preliminary points must be addressed.2 First, while Aquinas is clear elsewhere in his corpus that the activity of every being is [End Page 44] for the sake of an end,3 in the Fifth Way he narrows his focus to a specific class of beings: “things lacking cognition, namely, natural bodies.” The kinds of beings he has in mind when he refers to “natural bodies” (corpora naturalia) are physical, nonliving beings like wood, stones, fires, water, as well as physical, living beings like plants, animals, and even human beings.4 However, the scope of the Fifth Way extends only to those natural bodies which lack cognitive powers. At the very least, then, the natural bodies referred to in the Fifth Way include beings like fires and plants, though some interpreters also include the functional parts of animals in this category.5 It is the end-directed actions of these kinds of beings that interest Aquinas in the Fifth Way. For the sake of simplicity, throughout the paper I will use the phrases “natural body” and “natural bodies” to refer only to those natural bodies which are the subject of the Fifth Way, that is, those which lack cognitive powers. Second, questions have rightly been raised concerning the validity of the Fifth Way, as it appears to fall victim...