There’s a deep intimacy between Aquinas’s proof for the existence of God from natural teleology and Berkeley’s account of the world as divine language. Let’s consider them each in turn, and then reflect a bit on their interrelations.
The proof from natural teleology comes in the famous discussion of the Five Ways in ST 1.2.3. A preliminary observation: yes, these are in fact proofs, despite the assiduousness with which some recent Thomists have sought to avoid that conclusion: “Deum esse quinque viis probari potest” (Ibid.). I see no possible way of interpreting “probari” as not at all involving rational demonstration. This doesn’t mean, however, that Aquinas thinks that this kind of demonstration, while engaging natural faculties for knowing, is available apart from revelation. In the Treatise on Faith, he goes so far as to declare that pagans’ attempts to speak about God fail “omnino totaliter” (ST II-II.2.2.ad 3).
The fifth of these proofs is essentially an inference from the intelligibility of creation to an intelligence who stands behind it. “The fifth way,” Aquinas writes, “is taken from the governance of things.” That is, some things that lack cognition still “act with regard to an end (propter finem), which is apparent from the fact that they act always or frequently in the same manner…whence it is clear that it is not by chance, but by intention that they arrive at the end.” It’s important not to confuse this argument with arguments from “irreducible complexity” made on God’s behalf by advocates of Intelligent Design. I lack the competence to pass judgment on those arguments, but they have nothing to do with the problem to which Aquinas directs our gaze here. He has his eye on a much wider and more ordinary field: do you ever notice, he effectively wonders, that even inanimate objects seem to behave as though they have intentions or aims? As C.S. Lewis points out in The Discarded Image, the medieval favored metaphors of will (the stone longs to return to the earth), whereas we talk in terms of the even less plausible metaphor of intelligence (the stone obeys the law of gravitation), but both idioms capture the strangeness of the world: natural objects, themselves pretty clearly not intelligent, belong to a world of overwhelmingly intelligibility.
Aquinas goes on to observe that things without cognition only arrive at an end when directed by something with cognition (like an arrow by an archer). Intelligibility cascades downward from intelligence to what it orders; it doesn’t he insists, well upwards from the unintelligent. We might wonder if modern physics or evolutionary biology hasn’t refuted this line of thought (doesn’t matter simply spontaneously organize itself in accord with natural laws? Doesn’t natural selection blindly mold simpler life forms into more complex ones?). This intuition rests on a confusion, born from taking something for granted: most fundamentally, natural order only seems spontaneous if you take for granted the presence of the natural laws themselves. But why the actual world and not a much less interesting alternative? Aquinas is unwilling to take the fact of order for granted; he agrees with Berkeley that “a blind agent is a contradiction,” that action is for an end, and that an end is something intended. If this is right, then, “there is something intelligent, by which all natural things are ordered to an end, and we call this God.”
Berkeley was likewise struck by the excessiveness of natural order, which he insisted could only be explained as a manifestation of intelligence – not yours or mine, of course, but God’s. His most detailed discussion of this problem comes in Alciphron, where Euphranor observes, “From motions, therefore, you infer a mover, or cause: And from reasonable motions (or such as appear calculated for a reasonable end) a rational cause, soul, or spirit” (4.4). But the motions of nature are even more reasonable (sc. manifesting a wise ordering) than human motions: “doth it not follow then, that from natural motions, independent of man’s will, may be inferred both power and wisdom, incomparably greater than that of the human soul?” (4.5) But the free-thinker Alciphron objects that ascriptions of personhood to whatever causes natural phenomena are far-fetched: “I have found that nothing so much convinces me of the existence of another person as his speaking to me”; but, “you will not, I suppose, pretend that God speaks to man in the same clear and sensible manner, as one man doth to another” (4.7).
Euphranor seizes the nettle in the objection, albeit gradually. He suggests that they think about the perception of distance, which is complicated by the fact that we perceive the three-dimensional manifold of space by way of a two-dimensional image projected onto the retina. That is, distance is “a line turned end-wise to the eye,” which consequently cannot “project more than one single point on the bottom of the eye.” As such, “the appearance of a long and a short distance, is of the same magnitude, or rather of no magnitude at all, being, in all cases, one single point” (4.8). But this means that distance itself isn’t “immediately perceived” (4.8). Rather, we infer distance from the relative sizes of objects: “I find by experience that, when an object is removed still farther and farther off, in a direct line from the eye, its visible appearance still grows lesser and fainter: And this change of appearance, being proportional and universal, seems to me to be, that by which we apprehend the various degrees of distance” (4.8). But notice that the connection b/w distance and “faintness” isn’t (logically) necessary; the latter only suggests the former by way of constant conjunction (4.8). (Optics accounts for perception of distance in terms of the angle of light’s reflection, but that’s not what we use in inferring distance, 4.8.)
It follows from this that “the littleness or faintness of appearance…can no more suggest different degrees of distance…to the mind, which hath not experienced a connexion of the things signifying and signified, than words can suggest notions before a man hath learned the language” (4.9). (Berkeley at once approaches and stiff-arms Kant’s theory of the transcendental aesthetic, which argues that to experience anything at all is to experience it in space. It’s not a difference, though, about the contribution the mind makes to the perception of space, but rather about whether that contribution is innate and immediate or acquired and gradual.)
Our perceptions of light and shade signify (come to count as perceptions of) changes in distance, but they do so conventionally. Euphranor thus feels entitled to conclude, “It seems the proper objects of sight are light and colours, with their several shades and degrees; all which, being infinitely diversified and combined, form a language wonderfully adapted to suggest and exhibit to us the distnaces, figures, situations, dimensions, and various qualities of tangible objects: not by similitude, nor yet by inference of necessary connexion, but by the arbitrary imposition of Providence: just as words suggest the things signified by them” (4.10). That is, light and color signify visible objects. With this, Alciphron finally gets it: “I see, therefore, in strict philosophical truth, that rock only in the same sense that I may be said to hear it, when the word rock is pronounced” (4.11).
Oddly, in Alciphron Berkeley explicitly restricts the “divine-language” thesis to visual phenomena; the other senses lack sufficient “articulation, combination, variety, copiousness, extensive and general use, and easy application of signs” to qualify as a language in this sense (4.12). This, it seems clear to me, is a particularly egregious human parochialism on Berkeley’s part, owing to the fact that vision is by far the richest part of our sensory experience of the world. If we had a canine auditory and olfactory system, however, I doubt very much that Berkeley would have found this a remotely plausible claim.
Fortunately, he eventually seems to have overcome this prejudice, whether consciously or not. When Berkeley reprises the divine language argument in the Siris, he expands it to include all of the senses, and also demonstrates its classical pedigree: “There is a certain analogy, constancy, and uniformity in the phaenomena or appearances of nature, which are a foundation for general rules: and these are a grammar for the understanding of nature, or that series of effects in the visible world, whereby we are enabled to foresee what will come to pass, in the natural course of things. Plotinus observes, in his third Ennead, that the art of presaging is in some sort the reading of natural letters denoting order” (§252). He goes on to write, “The phaenomena of nature, which strike on the senses and are understood by the mind, form not only a magnificent spectacle, but also a most coherent, entertaining, and instructive discourse; and to effect this, they are conducted, adjusted, and ranged by the greatest wisdom” (§254).
Aquinas argues from the inescapability of treating the world as intelligible to the fact of a superintending intelligence who renders it so; Berkeley argues from the inescapable fact of treating the world as significant to a speaker who signifies by way of it. John Roberts captures the essence of this argument beautifully: “According to Berkeley, the necessary precondition of having any kind of knowledge at all is the adopting of the personal stance—not to this or that particular thing but to reality as a whole” (A Metaphysics for the Mob, 83).