Faith and Reason

This paper reasons that although Cleanthes and St. Thomas Aquinas offer different descriptions of nature itself, their attempts to prove the existence of God by means of teleological arguments are complementary. It examines in detail the related analogies that the two philosophers use to infer the existence of God. It ultimately argues that Cleanthes’s and Aquinas’s arguments are equally flawed in their conclusion that God exists.

Hume’s Cleanthes and Aquinas’s Fifth Way each present a version of the argument from design. An argument by design asserts that the empirical study of nature offers evidence that the world and its parts have purpose and direction.1 Advocates of the theory conclude that the world is designed. Thus, both Cleanthes and Aquinas argue that from the smallest blade of grass to the largest mammal on the planet, every part of the natural world is deliberate and designed. Naturally following this belief is the need for a designer of the natural world. This designer, both Cleanthes and Aquinas assert, is God.2

Although their proofs for God’s existence are essentially the same, the two philosophers’ depictions of nature differ considerably. Cleanthes’s account of the natural world is mechanistic. From this perspective, everything in the world follows certain natural laws, regardless of size or complexity. In fact, Cleanthes asserts that the world is “nothing but one great machine” where closer examination reveals “an infinite number of lesser machines” that regress to a point that even intelligent human beings cannot observe and understand.3 Therefore, in the same way that a desk lamp and a stadium floodlight are different objects built to operate in a similar way, so too in nature, a small flower and a large forest are built to operate in a similar way. On the other hand, Aquinas describes the world in terms of “natural bodies” that lack any type of intelligence or knowledge.4 A natural body, to Aquinas, could be anything from a bit of algae to an entire lake of water. Evidently, the two philosophers’ views of nature portray the world in to very distinct ways.

However, despite differences in terminology describing the world, both Cleanthes’s and Aquinas’s a posteriori methods lead them to the conclusion that all of nature has purpose and is therefore designed. Cleanthes argues that from the “one great machine” to the smallest machine imaginable, all have “an accuracy” about them.5It is this mechanical accuracy, Cleanthes maintains, that allows the parts and the whole of nature to act for a purpose, as “means to ends.”6 For Cleanthes, it follows that there must be an “Author of Nature,” a designer, who creates such accuracy of function.7 Aquinas agrees that nature acts for a purpose. He believes that, although natural bodies may lack any internal knowledge,8 they still “act for an end” in the world.9 For instance, rain falling from the sky will nurture plants, which in turn will transpire water into the air, which in turn will fall from the sky as rain again. Aquinas does not believe it is an accident that natural bodies, such as water in all its forms, act for specific, unchanging purposes.10Indeed, he argues that the natural bodies have been designed in order to reach their ends.11 Therefore, despite their striking differences in descriptions of the natural world, both Cleanthes and Aquinas advocate a fundamentally similar teleological argument.