This argument has a long history but perhaps its most famous exponent was William Paley, the English theologian and philosopher. Briefly, his argument, which pre-dated Darwin's Origin of Species by 57 years, was that, if you found a watch on a piece of heathland, the most logical conclusion would be that someone had dropped it there and that it had been designed by one or more watchmakers and not by natural forces.
And of course, this is unarguable for a watch, for the simple reason that there is no other mechanism which could explain the watch's production, nor how it came to be where it was found. That explanation requires no mystery; there is nothing required which can't be readily understood and certainly there is no need to include an unproven supernatural hypothesis in the explanation. The explanation that a watch was designed by a watchmaker is complete and the most parsimonious answer available.
And, with the state of our knowledge of biology and biological systems in 1802, there seemed to be no reason why this analogy did not apply to living animals as well. Living animals appear to be designed in that they have component parts which need to be arranged in the right way, though, curiously, there are no wheels in nature so any movement has to rely on levers with lots of pushing and pulling, acceleration and deceleration and not the far more efficient rotary action of wheels (imagine a car with legs!) but that's by the by.
Now, what purpose does a living animal have which is in any way comparable to the utility value of a watch? Living things exist only to produce other living things. Not so watches. Watches have a very specific purpose and that is to keep an accurate record of the passage of time.
There is an even more fundamental way in which watches are not like living things. Watches do not need elaborate mechanisms for finding their own energy source and to avoid becoming some other timepiece's energy source; they do not need excretory and circulatory systems to supply energy to its component parts and to carry away the waste, and, most significantly, watches do not need mechanism for finding mates and for producing and caring for offspring. Because they do not need any of these things they do not need sensory, reproductive and locomotory systems. And because they are not self-replicating, they need no mechanism for replicating information and passing it on to the next generation.
They don't need any of these things because they are designed and made by humans, for humans and humans provide their energy to them by winding them up. Without humans, watches have no purpose, no function, and no existence. Watches are merely human artefacts. Living creatures existed before humans and would undoubtedly exist without us. For the most part, living creatures are self-reliant and self-replicating because they have no designers and have no purpose other than existing for their own sake.
Moreover, if we look inside the watch we would not find any redundancy in the design. There would be no cogs spinning purposelessly away, no springs holding back levers for no reason at all, no overly elaborate mechanisms using several cogs and levers where one or two would do, no mistakes having to be compensated for by hugely inefficient work-arounds and no evidence of earlier designs still included but having no current function at all. The watch would be efficiently and accurately designed with obvious intelligence by someone who had a complete over-view of the purpose of his design and who knew how to make it as simply, and therefore as efficiently and accurately as possible. Additionally, if you were to look in different models of watch made by this watchmaker you would certainly see the same solutions used to overcome the same engineering problems; you would see the same springs, cogs, levers and bearings being used in the same way. You might even see exactly the same mechanism, just in a different case.
Unlike watches, living things have masses of inbuilt redundancy. The DNA of most living things is vastly more than is needed. There is DNA which does nothing other than produce copies of itself, for example. There is DNA which is added to the ends of chromosomes for no good reason because of a flaw in the copying mechanism and which just keeps being added to. There are vestigial organs to be found in most species, like evidence of legs in whales and the human appendix. There is evidence of work-arounds for earlier mistakes such as a complicated neural function to compensate for the blind spot in the mammalian eye because the wiring of the retina is backwards. And of course there is the ludicrous path taken by the recurrent laryngeal nerve, especially in the giraffe.
There is evidence of repeated new 'designs' of structures like wings and eyes and not the re-use of earlier solutions, such as a watchmaker would use. No intelligent watchmaker would think to re-design springs and cogs each time he decided to make a new watch.
In short, living things show evidence of design, but not of intelligent design.
So, does that apparent design point to a god, but just not a very intelligent one perhaps, or one with a fixation with beetles, of which there are some 500,000 different 'designs' alone?
What Paley, and those who were convinced by his argument, which incidentally included a young Charles Darwin, did not appreciate, in addition to all the redundancy, and in addition to failing to appreciate that watches have an obvious purpose which is not paralleled by living things, was that design does not necessarily indicate a designer, nor intelligence. This was never more than an argument from personal incredulity - I can't understand it therefore it must have been a god. They failed to appreciate this not because they were stupid or dishonest; they could only work with the state of knowledge of the times. They failed to appreciate it because they lacked one essential piece of knowledge, because science had not discovered it then.
What they failed to appreciate was that a natural process exists which can explain ALL these things, and which does not include an unexplained mystery for which no hypothesis can account, nor does it require magic. All the components of this system can be seen and understood, just like all of the components of the system for making watches can be seen and understood. No mystery, no magic and no supernatural component need be included in the explanation.
The explanation, as Charles Darwin and Alfred Russell Wallace showed in 1859, is natural selection. Natural selection by a selective environment from amongst variants of a self-replicating system which produces variations on a basic theme, is BOUND to lead to the appearance of systems which superficially look designed for the purpose of living and reproducing in that environment. Design is not the sole prerogative of intelligence. Design can also be performed by nature provided the thing being designed is self-replicating in a selective environment in which it competes with other living things and especially with variants of itself.
And given the system in which natural selection operates, the result is inevitable.
Natural selection is the most parsimonious explanation both for the appearance of design and for the appearance of a stupid designer. Living things look exactly as you would expect them to look if designed by a utilitarian, mindless, purposeless design process given direction only by the environment in which it operates.
Now that we can stand on the shoulders of giants like Darwin and Wallace, we can see further than other men. We can now see further then the Bronze Age goat-herder who thought up the creation myth and who couldn't even see over the horizon and thought the earth was flat.
We can see now that there is nothing supernatural required and nothing supernatural involved. (Tweet this)
And we can say "Wow! This is vastly more wonderful, more complex and more majestic than the prophets and priests told us" and we can ignore the ignorant gibberings of superstitious simpletons who insist it was all the work of their own small gods and the clamour of the parasitic charlatans who feed off their ignorance.