Hume's work Dialogues Concerning Natural Religion is concerned with whether we can deduce evidence regarding theological matters, God specifically, based upon observation and reasoning. The three characters - Cleanthes, Demea and Philo all hold contrasting views in the debate. Cleanthes believes that God is comprehensible and we can deduce things about God and related matters. Philo believes God is incomprehensible and anything that's related cannot be figured out. Demea also believes that God is incomprehensible, but unlike Philo, he doesn't care much for this topic. Cleanthes relied on the argument from design in an attempt to prove to Philo and Demea that it is possible to have knowledge of theological matters based on reasoning and observation. According to Cleanthes, the world which he thinks was created by God, is a great big machine that can be divided, then subdivided into countless numbers of smaller machines. Machines as we know it are impressively intricate and are built by man. The universe, like a machine, can be partitioned into infinitely small units but have intricacy far beyond what is capable of human contrivance. Continuing, Cleanthes states, "Since therefore the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble". (15) In a simple sense, Cleanthes is arguing a posteriori that since intricate machines are made by clever humans, then the world too, which is intricate, was created by God. Philo, the skeptic of the group, rebuts with a number of criticisms at Cleanthes' argument that "like effects prove like causes," (34) particularly in the claim that God is infinite.
Philo's foremost objection attacks Cleanthes' claim of God being infinite. Seeing that Cleanthes had stated the creation process as an infinite chain of cause and effect, Philo denounces this by claiming that the chain is not infinite because God was pointed to as the original creator of everything. In addition, the argument is made that since like effects have like causes, God must have finite capabilities and features because he is like humans. Therefore, Philo is able to say God is finite and Cleanthes must "renounce all claim to infinity in any of the attributes of the Deity." (35) Philo further fortifies his objection by saying that God's existence would be questioned if Cleanthes counter argued that God is not like humans and therefore he is infinite.
As we know it, Cleanthes' argument from design revolves around "like effects prove like causes." (34) Using this statement, Cleanthes noted that intricate things are made by minds that are similar to but greater than those that are produced, which is logical. However, as Philo objects, since God has a mind that is similar to humans because they are like causes, then God must be someone that is more clever and intricate but still bound to limits like humans. If God is bound to limits like man, then he too is not infinite. "Like effects prove like causes" (34) also calls forth Cleanthes' explanation of the chain of creation and how it is infinite. Philo is quick to point out that Cleanthes' so called infinite chain of creation stops at God as the ultimate creator, hereby proving Cleanthes wrong in either that his argument from design is flawed, or his claim that God is infinite. If God himself was not created by another entity, then he cannot be infinite. Using the logic from the argument from design, one can reason that since God is like humans, than he too must have been created by some being greater than him if his existence in the chain of creation is to be infinite. Should Cleanthes corrected himself by saying God is not similar to humans thus not eliminating the possibility that he infinite, Philo would question who then in fact is the ultimate creator or if one even exists.
Philo has obliterated Cleanthes' claim that God is infinite beyond doubt. Rather than raising a separate counter argument in response to Cleanthes, Philo simply uses Cleanthes' argument from design to strike down the notion that God is infinite and quite possibly the logic of the argument from design itself. The argument from design by itself is not wrong but as Philo shows, it can be used to discredit much of