I take it that the design argument, as expressed by William Paley, is that an item such as a watch, which "its several parts are framed and put together for a purpose" intrinsically raise the presumption that:
...and that as the universe in all its glory exhibits a huge amount of symbiosis and design, that it too must have had a maker.there must have existed, at some time, and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction, and designed its use,
Paley's presumption about the watch is only right if you construe it in the broadest possible sense. The physical artefact we think of as "a watch" appears to have a single designer (or a small team), but this isn't the whole story: the "ontological concept" of a watch - which is what Paley has to be referring to - would be well beyond the comprehension of any single human brain (or small collection thereof).
The invention of a watch assumes the the following inventions:
(a) the very notion of "time"
(b) a numbering system
(c) a horological system (ie 12 hours of 60 minutes of sixty seconds)
(d) metallurgy
(e) glass
(f) the spring
(g) the wheel
(h) the idea of cogs
(i) miniaturization techniques
... and so on. Each of these pre-existing inventions itself assumes a number of prior inventions, and so on and so on. Each of those concepts is a "crane" without which the idea of a watch could not even be conceived.
The invention of a watch is the aggregation of a huge number of tiny inventions over a period of say 4000 years, almost all of which are purely coincidental to the "purpose" Paley sees in a watch (for instance, the devisors of the wheel probably had no conception of time at all).
The point is not to say "therefore there can't be a God" - but rather to stand back and observe that a single inventor faced with inventing a watch from scratch has an absolutely superhuman task. I venture to say that it simply could not be done by any single mortal mind.
But that isn't to say the watch hasn't been wholly designed by mortal minds. Clearly, it has. But this puts the teleological argument in a different light. One might draw a conclusion opposite to Paley's: The more design an item exhibits the less likely it is to be created by a single designer at a single time with a single purpose.
And if a watch is a stupendously clever thing, what about a whole universe!
The teleological argument, therefore suggests two alternatives:
Even if there is no evidence to support (a), the teleological argument presents no empirical evidence for (b). It simply says, if (b) is true, then it is a fairly safe assumption that the mind in question was pretty extraordinary.(a) the universe is so complex that no single mind acting alone could possibly have created it, and it must be explicable as the result of a lot of smaller, unconcerted "inventions" which themselves are the result of smaller unconcerted "inventions"; or
(b) a single mind did it, but to do so that mind had to be, to all intents and purposes, omniscient (and probably omnipotent too).
That's the easy part. Establishing The Single Mind is a taller order (and note, you're back to square one, since this is what you were trying to prove in the first place). In order to establish The Single Mind you still need to give a credible account for the existence of this single creator, and in fact your problem is if anything worse, since ipso facto this Single Mind must itself be so cleverly designed that it can only have been designed by a designer ... well, you can see the moebius loop for yourself, I hope. (if you invoke method (a) at this point - which is open to you to do - you still need to explain why you didn't do this at the earlier stage and just leave out The Single Mind).
Leaving aside the difficulties with (b), conclusion (a) is far more plausible anyway. This is effectively the Evolutionary programme. Dan Dennett argues it very well in his book "Darwin's Dangerous Idea", but I don't want to get into proposing counter arguments to Christianity, so will leave it at that.
I have another way of explaining why it's more plausible. Two actually.
1. King's Cross Station at Rush Hour: I am lucky enough to live and work in London, one of the most fascinating cities on the planet. Every day I have to negotiate Kings Cross underground station at Rush Hour. If you haven't done it, it will be difficult to comprehend what an awesome spectacle this is. There are five underground and at least 9 (and 3/4s!) overground lines passing through the station - and it's currently being extensively re-designed, above and below ground, as well. I would say that a thousand people pass through the (fairly narrow) underground concourse every minute during the hour and a half of rush hour each morning (actually more, since that's only 90,000 people). All travelling fast, places to go, anxious to spend as little time as possible in the station. Lines of pedestrians flow through ticket barriers, interweave, head in different directions, down different escalators, to different platforms, on and off trains, and yet the collision rate is astoundingly low.
Now, imagine the job of calculating and plotting, in advance, the trajectory of every individual in that concourse in just a ten minute period - building, if you like, a computer model of the path every person must take to get from their carriage or exit to their destination carriage or exit, without colliding with any other person. Rather like plotting the trajectory of grains of sand in a sand storm: It would be a hugely complex task, requiring hours of sophisticated programming and not inconsiderable computer processing power. Now expand that to the 7 million passengers who travel on the underground everyday. Or every one of the 14 million commuters each day in London across all modes of transport. The complexity of the problem expands geometrically the more people and possible journeys you introduce, rather like the proverbial grains of rice on squares of a chessboard.
Yet it is perfectly possible to solve this problem without that complex engineering (between us, we commuters manage it every day in London, after all): each person has a single task: get yourself from point A to point B without colliding with anyone. Adjust your trajectory as you go to ensure this. This time, there is no geometric expansion of the problem; each additional person needs to follow the same, simple algorithm. In fact, a few people can have an even simpler algorithm: get yourself from point A to point B irrespective of collisions" and it is still likely they won't collide with anyone else (as long as they only encounter "avoiders" who get out of their way).
The analogy is the same: the entire, symbiotic, dynamic, adapting functioning of the universe could be the product of some initial, utterly, inconceivably, brilliant design, or rather it could be the result of the aggregation of trillions of individual reactions, none of which by itself is particularly remarkable.
2. Communist China and the Wild West: Consider two extreme theoretical models of an economic system:
(i) a centrally planned economy, where a central thinker projects production, likely demand, necessary skills in the workforce, allocation of resources, plans cities, moderates behaviour, and anticipates necessary inputs and outputs throughout the economy
(ii) an anarcho-laissez-faire economy, where the government says to the population, broadly, "ok, fellahs: away you go!"
Now, which of these is more complex to design and manage? Which is more efficient and effective? (Hint: If you're not sure, read Wild Swans before answering!)