It is no secret that intelligent design is a reiteration of
centuries millienia old ideas. All that is really new is that its proponents are less than sincere in what they are peddling and perhaps ignorant of the history of natural theology.
While natural theology has a long history, it seems (to this newbie in the field anyway) it was most well-articulated by the late 18th century Anglican theologian William Paley. Paley was not known for his original ideas, apparently, but for his ability to write well and convey ideas to the public. His last book, Natural Theology (1802), historically speaking, seems like a triumphant last gasp of the field.
Upon reading Natural Theology, I was struck by how quickly the famous watchmaker analogy pops up: the first page! Most readers have probably already heard creationists and intelligent design proponents argue with this metaphor, sometimes with a tornado creating a 747 from a junkyard (have to keep it modern, right?). While this argument is absurd nowadays, I think it worked well back in 1802 when the two competing theories were basically creation and chance. (Thankfully, over the next century, the theory of evolution offered a superior alternative). 
While the watchmaker analogy dates back to at least Cicero, I had never read its articulation by Paley until reading the book and it is eerie how similar the argument really is to intelligent design, even with ~200 years of separation. It is almost verbatim!
Here is it reproduced in full:
IN crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that, for any thing I knew to the contrary, it had lain there for ever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, that for any thing I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? why is it not as admissible in the second case, as in the first? For this reason, and for no other, viz. that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose, e. g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day: that if the different parts had been differently shaped from what they are, of a different size from what they are, or placed after any other manner, or in any other order, than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it.
Replace the watch with the flagellum and you have Michael Behe’s <a href=http://en.wikipedia.org/wiki/Irreducible_complexityirreducible complexity argument exactly. While the argument has become more biologically-inclined with time, and more rooted in math and biochemistry, the gist of the argument has remained unchanged. Kinda pathetic, isn’t it?
Paley continues by providing details of watch mechanics and how inconceivable it would be for the watch to be a product of chance. He also raises possible problems with the analogy and refutes them. (He also begins to weirdly introduce the possibility of watches reproducing themselves and what would be the implications of such a property.) I won’t delve into those details, however.
To ground his analogy in reality, Paley immediately applied his argument to the all-too-common eye. Evidencing the argument from design with the eye dates back to at least Socrates and while to continue using it in Paley’s time was understandable, for people to keep using the eye today is simply laughable. (For remember, Darwin basically took care of the argument in the Origin.)
One thing that struck me was the language Paley uses to address the design of the eye.
Besides that conformity to optical principles which [the eye’s] internal constitution displays, and which alone amounts to a manifestation of intelligence having been exerted in the structure; besides this, which forms, no doubt, the leading character of the organ, there is to be seen, in every thing belonging to it and about it, an extraordinary degree of care, an anxiety for its preservation, due, if we may so speak, to its value and its tenderness. (p23)
Paley infers from the design of Nature the benevolence of God and he believes this is best exemplified by the eye’s secondary features. The eye is not blatantly exposed upon the body, say located on the hands or something, but is instead within the bony skull and protected by an eyelid. This is evidence that God “cares” and “preserves” the organ through his designs. God is clearly benevolent. (Unlike modern intelligent design proponents, Paley is not afraid to argue in public that the argument from design allows us to infer the properties of God.)
Perhaps the most fascinating thing I have found while reading Paley is that he actually addresses the argument of unintelligent design!
He alludes to the argument from unintelligent design at the beginning of the book:
Neither, secondly, would it invalidate our conclusion, that the watch sometimes went wrong, or that it seldom went exactly right. The purpose of the machinery, the design, and the designer, might be evident, and in the case supposed would be evident, in whatever way we accounted for the irregularity of the movement, or whether we could account for it or not. It is not necessary that a machine be perfect, in order to shew with what design it was made: still less necessary, where the only question is, whether it were made with any design at all. (p8)
I am not sure this constitutes a valid argument, but he clearly did not deny that living beings were sometimes imperfect. But God is omnipotent and omniscient, right? Why would he introduce poor designs? Paley has quite the clever argument – one I had never encountered before.
First the set up:
In the configuration of the muscle which, though placed behind the eye, draws the nictitating membrane over the eye, there is, what the authors, just now quoted, deservedly call a marvelous mechanism. I suppose this structure to be found in other animals; but, in the memoirs from which this account is taken, it is anatomically demonstrated only in the cassowary. The muscle is passed through a loop formed by another muscle; and is there inflected, as if it were round a pulley. This is a peculiarity; and observe the advantage of it. A single muscle with a straight tendon, which is the common muscular form, would have been sufficient, if it had had power to draw far enough. But the contraction, necessary to draw the membrane over the whole eye, required a longer muscle than could lie straight at the bottom of the eye. Therefore, in order to have a greater length in a less compass, the cord of the main muscle makes an angle. This, so far, answers the end; but, still further, it makes an angle, not round a fixed pivot, but round a loop formed by another muscle; which second muscle, whenever it contracts, of course twitches the first muscle at the point of inflection, and thereby assists the action designed by both.
The structure of which Paley is speaking is the trochlea of superior oblique (Fig 1).
Here Paley liberally employs analogies to human-made inventions like pulleys and observes that designs like this may be “peculiar” and counter-intuitive. While the design works, and in some instances their peculiarity enhances the design, he wonders why God would invent such “contrivances.” These seem needlessly complicated as Paley explains:
Why this circuitous perception; the ministry of so many means; an element provided for the purpose; reflected from opaque substances, refracted through transparent ones; and both according to precise laws; then, a complex organ, an intricate and artificial apparatus, in order, by the operation of this element, and in conformity with the restrictions of these laws, to produce an image upon a membrane communicating with the brain? Wherefore all this? Why make the difficulty in order to surmount it? (p26)
In other words, why would God make a burrito so incredibly hot only to create a tongue that felt no pain? Well, not exactly, but again, why would God make his work more difficult than he needed to?
Contrivance, by its very definition and nature, is the refuge of imperfection. To have recourse to expedients, implies difficulty, impediment, restraint, defect of power.
Why would God design an inferior product? Paley realizes addressing this problem is crucial to the argument from design as it strikes at the heart of God’s nature. “Contrivance” requires an explanation.
It is only by the display of contrivance, that the existence, the agency, the wisdom of the Deity, could be testified to his rational creatures. This is the scale by which we ascend to all the knowledge of our Creator which we possess, so far as it depends upon the phenomena, or the works of nature.
Huh? How so?
Whatever is done, God could have done without the intervention of instruments or means: but it is in the construction of instruments, in the choice and adaptation of means, that a creative intelligence is seen. It is this which constitutes the order and beauty of the universe. God, therefore, has been pleased to prescribe limits to his own power, and to work his ends within those limits. The general laws of matter have perhaps the nature of these limits…
These are general laws; and when a particular purpose is to be effected, it is not by making a new law, nor by the suspension of the old ones, nor by making them wind, and bend, and yield to the occasion…
… but it is, as we have seen in the eye, by the interposition of an apparatus, corresponding with these laws, and suited to the exigency which results from them, that the purpose is at length attained.
Have you ever had an art of English teacher limit what you could work with on a certain project? For example, right now in my creative writing class, we have to write a poem and there are quite a few constraints: it has to be about a place we have been, it has to contain list, and we can use only one adverb and abstract noun. The argument is that such limits force us to be more creative, i.e., we have to work around them.
This is the exact argument Paley ingeniously, I think, employs. God created the laws of physics and decided not to violate them by “making a new law” or simply suspending them, but instead designed around those laws.  The trochlea pulley seems weird and unnecessary, for God surely could have just fixed the problem he faced, but he may have had to temporarily suspend or change a natural law to enact a solution. Instead, he used a simple machine, the pulley, to fulfill his will. Furthermore, we would readily recognize the pulley as an intelligently designed system, i.e., the essence of natural theology.
Is Paley’s constraint argument flawless? No, far from being so , but it is a unique way of looking at biological systems. It makes me wonder: Why do modern intelligent design proponents not resort to this? Perhaps they do and I just haven’t seen it, but because there is an obsession with God being perfect, many sympathizers may not agree that God chooses to not violate the laws he created and concoct imperfect designs? After all, miracles are a suspension of physical laws so why not just say the eye is a miracle and be done with it?
That kind of argument, incurious and unimaginative, would not satisfy Paley, I think. He is clearly delighted to examine how nature works. His book is littered with dozens upon dozens of examples, ranging from woodpecker tongues to sleep cycles. I feel as though most run-of-the-mill creationists see nature quite differently from Paley; in fact, I would argue that Paley sees the world as most biologists do: as a wondrous environment composed of “endless forms most beautiful” worthy of close investigation. 
Paley finds cleverness in nature. While he frequently says traits are “designed,” he also frequently states that they seem “contrived.” In that sense, I would label Paley’s argument not as “intelligent design,” but as “intelligent contrivance.” I believe this serves two purposes: 1) It properly connotes Paley’s view of nature as cleverly created, not boringly and neutrally “designed.” 2) Paley’s argument is quite Panglossian in that he believes the world is the work of a benevolent deity and everything serves a “good” purpose, even diseases.  Indeed, he says “the care of the Creator is seen where it is wanted.” I interpret this as the world being “contrived,” similar to how we would describe an artificial plot (the convenient placement of Old Spock on Delta Vega in the latest Star Trek film, for example). “Contrivance” conveys both cleverness and artificiality – the former an accurate presentation of Paley’s belief and the latter a criticism of the argument – a double-edged sword.
While natural theology’s premise is clearly wrong, Natural Theology offers an insightful view of pre-Darwinian biology. I was surprised by the sheer amount of examples Paley employs to bolster his argument. Nature is quite wonderful (obviously) and I am mighty pleased to learn that intelligent design and creationism, historically speaking, was not propounded by ignoramuses and liars, but were appreciated and articulated by people who, like modern biologists, saw the workings of life as breathtaking and marvelous. Paley was more a modern biologist than he was a modern creationist.
 Darwin’s theory of natural selection removed the need for creationism. We have also since learned that chance does play an essential role in evolution, but as “chance” was conceived in the 19th century, it was an implausible explanation.
 As I have not read Paley’s earlier work, I do not understand how Paley’s essentially deist argument is reconciled with Christian miracles. I suspect that Paley distinguished design from the acts of God in human history.
 Paley fails to properly address vestigial organs. He argues that vestigial traits are just traits for which we have yet to find a purpose; this was plausible in 1802, but it is now a disappointing mistake. I would have appreciated a clever argument á la Paley’s contrivance in design.
 @shiftingbalance notified me that John Maynard Smith and Richard Dawkins claim Paley’s legacy which I am glad to hear. I assume Dawkins discusses this in The Blind Watchmaker which I will be reading later this semester and I will report that when it comes up.
 Paley counters the argument from evil with a utilitarian response. For some reason, I had never encountered utilitarian apologetics, but I think Paley’s articulation of it is the best response to the problem of evil I have seen. I don’t think he refutes it or anything, but I prefer it to the odious free will argument.