In Part II of the Dialogues, Cleanthes presents a rudimentary design argument in response to Demea and Philo’s skepticism concerning the nature of God. Assuming the principle that like effects precede from like causes, Cleanthes asserts that the Universe sufficiently resembles a human artifact, by virtue of the adjustment of its parts to each other and the curious adapting of means to ends, so that we may infer that the Cause of the Universe resembles the human mind to a certain extent. Demea responds with disappointment that this is only an probabilistic, as opposed to a demonstrative, argument, while Philo casts doubt on the inference because he does not think it obvious that the Universe sufficiently resembles a human artifact. In most other cases where we infer similar causes from similar effects, we have had a great number of experiences with similar effects, while we obviously have no experience of the origin of the Universe. Furthermore, it seems presumptuous to assume that human intelligence is paradigmatic for all forms of intelligence, and it is risky to extrapolate our experience with the causes of a small part of the things that happen in the Universe to the cause of the Universe as a whole.
Cleanthes’ reply to these objections is rather interesting. He claims that it is not necessary to demonstrate the resemblance of the Universe to a human artifact, “because this similarity is self-evident and undeniable.” He compares Philo’s objections to “the abstruse cavils of those philosophers, who denied motion; and ought to be refuted in the same manner, by illustrations, examples, and instances, rather than by serious argument and philosophy.” (p. 54) In other words, Philo’s objections might be compared to those of skeptics who deny the existence of the external world. Famously, there is no knock-down philosophical argument that proves the existence of the external world. But this is not because its existence is in doubt, but because on the contrary its existence is so obvious and the belief in it forms in us so naturally that we can only ever respond to the skeptic by pointing to the immediacy of that experience. Similarly, Cleanthes claims that it is not appropriate to try to prove that the Universe is designed, but instead we should point again and again to those self-evident instances of design that everyone acknowledges. As an example, Cleanthes points to the eye: “Survey its structure and contrivance,” he challenges Philo, “and tell me, from your own feeling, if the idea of a contriver does not immediately flow in upon you with a force like that of sensation. The most obvious conclusion surely is in favor of design; and it requires time, reflection and study, to summon up those frivolous, though abstruse, objections, which can support infidelity.” (p. 55)
Ironically, Cleanthes can actually appeal to Philo’s own epistemology in support of this claim: “The declared profession of every reasonable skeptic is only to reject abstruse, remote and refined arguments; to adhere to common sense and the plain instincts of nature; and to assent, wherever any reasons strike him with so full a force, that he cannot, without the greatest violence, prevent it. Now the arguments for natural religion are plainly of this kind; and nothing but the most perverse, obstinate metaphysics can reject them.” (p. 56) Recall that Philo acknowledges the validity of human reason in the sphere of our direct experience, because the immediacy of that experience is powerful enough to overrule refined skeptical worries. But it seems that when many people observe the natural world the conclusion that it is designed does ‘immediately flow in upon them with a force like that of sensation.’
[Interlude: It seems that Hume was well aware of the forcefulness of the impression of design amongst most people. However, this did not assuage his skeptical worries. For one thing, this impression seems to be not quite on the same level of immediacy as our sense experience. As he puts it in his letter to Gilbert Elliott, “The Propensity of the Mind towards [the conclusion of design], unless that Propensity were as strong and universal as that to believe in our Senses and Experience, will still, I am afraid, be esteem’d a suspicious Foundation…We must endeavor to prove that this Propensity is somewhat different from our Inclination to find out own Figures in the Clouds, our Face in the Moon, our Passions and Sentiments even in inanimate matter. Such an Inclination may, and ought to be controul’d and can never be a legitimate ground of Assent.” (p. 26) In other words, the impression of design is not quite as forceful or immediate as the impression of the external world or the reality of motion, and given that we sometimes erroneously perceive order and design when there is none (like when we see figures in the clouds, or imagine that inanimate objects have intentions, feelings, etc.), we do need some argument for accepting design.]
Despite his claim that Philo’s objections are ‘mere cavils’, Cleanthes does accomodate them by attempting to demonstrate that we can reliably infer design even the apparently suboptimal conditions implied by those objections. As an example Cleanthes presents the following scenario:
Suppose, therefore, that an articulate voice were heard in the clouds, much louder and more melodious than any which human art could ever reach: Suppose, that his voice were extended in the same instant over all nations, and spoke to each nation in its own language and dialect: Suppose, that the words delivered not only contain a just sense and meaning, but convey some instruction altogether worthy of a benevolent Being, superior to mankind: Could you possibly hesitate a moment concerning the cause of this voice? And must you not instantly ascribe it to some design or purpose? Yet I cannot see but all the same objections (if they merit that appellation) which lie against the system of theism, may also be produced against this inference. (p. 54)
It seems obvious that if we were to experience such a phenomenon, we would immediately and rightly conclude that it was produced by an intelligent agent. And yet it seems to fall prey to all the objections Philo laid out in Part II: we would have had no prior experience of this celestial Voice, and it is not like any human voice by virtue of its intensity, extent and ‘translatability.’ Cleanthes concludes, therefore, that his design argument is untouched by Philo’s objections.
Hume describes Philo as somewhat embarrassed by this forceful response, but Demea chimes in with another interesting objection: the human mind and its sentiments are what they are because of the kind of world we must survive in, and these constraints clearly do not apply to God: “All the sentiments of the human mind…have a plain reference to the state and situation of man, and are calculated for preserving the existence, and promoting the activity of such a being in such circumstances. It seems therefore unreasonable to transfer such sentiments to a supreme existence, or to suppose him actuated by them…” (p. 58). It is true that God would not be motivated by any sort of fear of deprivation, or feel threatened by anything, but it seems that even a self-sufficient, all-powerful Being could coherently experience pleasure or express disapproval if His designs are not carried out.