The argument from design, also known as the fine tuning argument or the Teleological argument, is one of the most popular arguments for the existence of god. In essence, it holds that since the universe seems to be perfectly designed for complex life, it must therefore have been designed for just that reason.
One of the more basic forms in which this argument appears – used by such thinkers as Thomas Aquinas and William Paley – is based on observing the breathtaking complexity and apparent design in the natural world, and concluding that a) it looks designed because it is designed, and b) if it is designed, there must therefore be a designer – i.e. god. This same argument often piggybacks on science when its proponents use scientific methods to show that life is even more complex than had previously been thought. This is actually a surprisingly effective tactic because oftentimes, the more people find out about the complexity of a thing, the easier it becomes to convince them that the thing must have been consciously designed.
Another scientific variant of this argument suggests that if the constants of the universe (mass, energy, gravity, etc) had been even slightly different, nothing would exist – neither life nor even matter. The claim goes on to conclude (wrongly) that the universe must have therefore been very finely and deliberately tuned to allow for life to exist. This is commonly dubbed the ‘fine tuning argument’, and is one of the more commonly used arguments by contemporary religious apologists.
One good way to begin your rebuttal to such arguments is to point out the irony in the religious claim that meager flawed, intrinsically sinful humans are also somehow the center of the entire universe – indeed, the reason for the universe to exist at all. The reality, as we have scientifically discovered, is quite the reverse – we are simply a result of how the universe is, and not the other way around. It is therefore possible to say that the universe isn’t fine tuned for us, we are fine tuned to it, but it would be more correct to say that we are “it”. We are a part of this fine tuned universe, so any semblance of us AND the universe is simply made up, and only adds a false dichotomy to what is already an argument from ignorance.
The reason I call it an argument from ignorance is because the design argument is not supported by any real evidence. It asks questions – How could all of this have come to be? or How can you explain such infinite complexity? (perfectly good questions, by the way) and then proceeds to answer them (wrongly) by asserting that a supernatural deity must be responsible for it; as if all the empirical and logical heavy lifting had been done by simply making the assertion. Furthermore, this is a circular argument since it holds that the complexity and apparent design of the universe is evidence of a designer, who can himself be inferred from the complexity and apparent design of the universe.
But the main problem with the grand designer explanation is that not only does it fail to answer the question, it exacerbates it. An actual explanation is a clarification by means of reduction to simplicity, but the designer hypothesis does the exact opposite. Instead of rhetorically breaking down the complexity of nature to show what simpler components it is made of, it leaps from complexity to infinite complexity and asserts the existence of a supernatural designer. Then, when the natural question ‘who designed the designer?’ comes up, the religious will arbitrarily assert that this designer is eternal and does not require any explanation. To say that this designer does not require an explanation is to all but admit that you have none, which rather dismisses the validity of this supposed explanation in the first place. A police investigator claiming that the bank must have been robbed by a supernatural phantom is just as problematic as a physicist claiming that the universe was designed by a supernatural deity. It simply opens up more questions than it closes; kicking the can down the road and raising the stakes without addressing the issue. If you are so sure that the infinitely complex designer of the universe was not himself designed then why is it so difficult to accept the idea that our complex universe might have not been designed? You might as well save yourself the indignity of moving the goalposts and either accept that the universe might in some way be eternal or that it was caused by non conscious simple elements that we still don’t fully understand. Either one of these would be many times more likely than a supernatural designer deity.
At some point during this debate, you can all but expect your counterpart to try to turn the tables and ask how YOU can explain the complexity and apparent design in the universe. This gives you an opportunity to tell your counterpart that there are in fact many scientific explanations for this, but one way or another, if you want to be intellectually honest about it, you simply must admit that there are things you still don’t know. I am actually proud to admit this, since it is one of the best ways to prove that I am being intellectually honest. As long as we have no evidence to show why the constants are the way they are, for example, I do not know the answer – and neither do YOU, my dear religious counterpart, whether you are honest enough to admit this or not.
You might also want to remind your counterpart that just because we do not yet have a scientific answer, it does not mean there must be a religious one. There was a time where we did not have scientific explanations for lightning bolts, earthquakes, storms, comets, eclipses and diseases, but religious explanations for these phenomena were no less incorrect in ancient times than they are now. Similarly, just because we currently do not understand certain things, a religious explanation would be no more legitimate now than after we acquire more scientific explanations. A very clear line can be drawn throughout human history that shows a consistent replacement of religious explanations with scientific ones, and never in human history has there ever been a reversal of this.
Even before you begin to point out the many faulty designs in our universe, the argument from design fails in the same way, and for the same reasons, that the Zeus argument for lightning bolts and the Poseidon argument for storms at sea fail.