Theistic Apologists deploy several arguments to try to establish that a god(s) is necessary. In my humble opinion, the worst of all these arguments is the Fine-Tuning Argument. The Fine-Tuning Argument is essentially saying that the parameters of the universe as we know it are placed in such a way to allow life as we know it to exist. However, there are three fundamental flaws that make this easily the worst argument a theist could use to justify their deity(s).
First, when employing this argument, the theist is making the underlying assumption that the fine-tuning we see in the universe is the only possible way the universe could exist that would permit life. No justification for this is ever given, beyond the fact that if the fine-tuning were different, then things would be different; an example of a counterfactual conditional. Simply because things would be different does not mean that life or a universe could not exist. They may not be as we see them today, but that alone does not mean that the possibility for life and a universe are dependent on the fine-tuning of the universe as we know it. This is an unjustified claim built into the argument that should be challenged. Beyond that, the theist also has not shown that the fine-tuning of our universe could be anything different. It could just as easily be that all possible universes have the same fine-tuning.
Second, this argument does not take into account evolution. Built into this argument is the assumption that we (either humans or all life on this planet) perfectly fit. The Earth is just the right distance from the Sun, the Moon is just large enough to keep our axis stable, Jupiter is just large enough and far enough away to keep us safe from space junk, etc… However, what the theist usually fails to account for in this picture is the 14 billion years of history the universe has gone through, 4.543 billion years of our planet’s own history, and ~4 billion years of life history on this planet. Most of the life history we see is shaped by selection and a lot of dumb luck thrown in for good measure. Essentially, it is asinine to say this planet/universe is fine-tuned for us. If anything, we are finely-tuned by the environment.
Third and by far the largest problem for this argument. As of the writing of this post, we currently know of one planet in our solar system that supports life. That life is supported mainly on its surface, and (except for Tardigrades), species can only survive in certain environments. There are seven other planets in our solar system (plus a few hundred moons) that do not support life (as far as we know now). There are a few possible other places in our solar system that might have life (i.e. Mars and a few moons around Jupiter or Saturn). Thus, out of several celestial bodies in our solar system, there are less than ten of them that could support life. Besides this, there is empty space between those celestial bodies wherein life cannot exist. Basically, whenever a theist tries to use the Fine-Tuning Argument, they are essentially saying; “Look at this earth size planet. It has one microorganism on it. Thus, the planet must be finely-tuned for the microorganism.” Any engineer would look at that system and conclude that it was poorly tuned if its purpose was for sustaining that microorganism. If this universe was fine-tuned for anything, it was fine-tuned for creating black holes and not life.
One objection to these objections could be if the theist is willing to admit their deity(s) is not omnipotent. Most apologists in the West would not dream of giving up that aspect of their deity. However, why would an omnipotent being need to fine-tune a system in the first place? Would it not be powerful enough to create a flawless system? In addition, if it were not powerful enough to create a flawless system, how could we say it is a god?
Another objection that Abrahamic Apologists could try is “The Fall” caused this. One problem I would have with this objection is that it could account for the planet earth, but why all the other celestial bodies and the rest of the universe? Why create such a universe that would be affected by two hairless apes on a rock orbiting a nondescript star?
There appears to be nothing redeemable about this argument. In fact, this argument could be far better used to show that there is not a single omniscient and omnipotent deity that cares about life (let alone humans) for the simple fact that this universe is not finely-tuned for us. Given just one of those two attributes (omniscient or omnipotent), a human fine-tuner could produce a universe far more hospitable for life.