Fine-tuning argument does not work for another reason : we simply don't know the number of universes and the mechanism that chooses the constants.
Basing on the reply I am not very certain of your exact position. I kind of suspect it is implying the multiverse response to fine-tuning. It suggests the reason for observed fine-tuning is because there are many universes in total, and only in the ones compatible with life can give rises to observers pondering upon the parameters. Therefore finding ourselves in a universe compatible with life is not a surprise. I.e. It is not statistically incredible because of the huge number of universes out there.
I have to say that answer is very problematic. It treats "I" or "us" as the outcome of a sampling process subjected to survivorship bias, which interprets the WAP as an Observer Selection Effect (OSE). This conceptual selection has to be done from a god's eye perspective. It makes the same mistake as the fine-tuning argument by mixing first-person reasoning with objective reasoning.
In my opinion, this actually justifies the fine-tuning argument. Furthermore, it hijacks the anthropic rebuttal (which should be a simple tautology based on consistent perspective thinking). It also leaves the door open for rebuttals such as Leslie's firing squad and the fine-tuned multiverse.
In a sense, the fine-tuning argument is still an ongoing debate because currently, anthropic reasoning is inadequate. It is filled with paradoxes and controversies. All popular assumptions (SSA, SIA) treats indexicals as the outcome of some sampling process, implying the OSE. My Perspective-Based Argument (PBA) is an attempt to change that.
I was thinking that probabilities cannot be assigned to our observed constants, given, say the hypothesis that the Universe has not been created by God. The Fine-Tuning Argument tries to update in favour if theism by observation of constants. For it to work we have to estimate the probability of our constants under the theistic hypothesis and its negation. I don't think it is possible.
This is an informal argument against the fine-tuned universe. The complete argument can be found on my website. The purpose is to show the importance of perspectives in reasoning, especially in anthropic topics. See my previous post for a summary.
I know this sounds ridiculous. But bear with me for a minute. I will prove it to you. The clue is in the history.
I have 2 parents, 4 grandparents, and 8 great-grandparents. This number keeps multiplying. 50 generations back, the theoretical upper bound for the number of my ancestors is about 10^15, way above the total number of humans ever lived. Of course, there would be significant overlaps in this mega family tree. At this scale, calling it a family web would no longer be a joke. Nonetheless, even with overlapping, it still means going back far enough, say around 1000AD, my direct ancestors would cover a significant portion of the world population.
My existence is the result of all those people’s reproductive success. That means any historical event that affected the lives of a moderate number of people must have unfolded exactly the way it did for the creation of me. If Alexsander lost the battle of Gaugamela, or Genghis Khan failed to unite the Mongol tribes, or Columbus did not reach the New World in 1492, I would not be here.
Why stop there? It can go even further and be more disturbing. For my existence, it is not enough that all my ancestors successfully produced offsprings, they had to produce the exact offsprings. Meaning in each case the exact sperm had to fertilize the exact egg. Couple this with the exponential growth of my family tree the chance of my existence is unfathomably small. Yet, here I am.
This is either a statistical miracle or, an unknown force has guided every aspect of the past to ensure my existence. The odd is too obvious. The history must be fine-tuned for me.
I can imagine how people would react if I tell them the above. They will say I am unbelievably egocentric and narcissistic. Why would history care if you are produced or not? Something could very well happen differently causing you not to be born. Big deal? More importantly, if the past is fine-tuned for you, am I just a by-product of that fine-tuning? I can use the same argument from my perspective and say history is fine-tuned for me instead of you. Safe to say it is not going to be well received.
Foreseeing these criticisms I decide to modify that argument a bit. I need more allies on this. So instead of focusing on the immediate “me”, extend it to “my kind”. Depending on how inclusive I want to be, that could mean humans, or life, or conscious beings, or complex physical systems, or maybe something even more general. On the other hand, to keep the probability low, extend the history further back. Consider the entire universe: all of its past up to the initial conditions and how the fundamental parameters came to be.
Now we have the argument known as the fine-tuned universe. It looks at the fundamental parameter of our universe and made an amazing discovery. They are all compatible with life's existence. Given the odds, "life" must be in some way significant to the universe. It is still the same egocentric and narcissistic argument. But this time, it is less obvious. Because everybody discussing it is"life". We are all on the same side.
Both arguments take a first-person perspective while presenting their evidence. I analyzed the historical events basing on their eventual effect on "my" existence. The fine-tuning argument analyzed all fundamental parameters according to their compatibility with life (our kind). There is nothing inherently wrong with doing so. However, we must realize this focus on oneself is perspective dependent. E.g. If another person analyzes historical events the same way I just did, he would analyze them based on their effects on him rather than on me.
From here, if I am to ask "why are all past events compatible with my existence?" it would be a perspective-dependent question. So it must accept a perspective-based answer. The answer is clearly "because I would always find myself exist". Reasoning from any perspective, it would always conclude the existence of its perspective center. That tautology is the Weak Anthropic Principle (WAP) response to fine-tuning.
However, proponents of fine-tuning argue that response is not a causal explanation of the fundamental parameters' value. Others criticize it for being unscientific. To that, I would say of course it is not scientific or causal. Because it is not answering a scientific or causal question. For those answers, the question should be objective/impartial. It should not be focusing on "me", or be perspective-dependent.
There are multiple ways to be impartial, but perhaps the easiest is to take a god's eye perspective, to reason with "a view from nowhere". I personally think that is not the best approach but that is a topic for another day. The important thing here is to recognize "why are the fundamental parameters compatible with life?" and "why the parameters have these values" are two different questions. They are formulated from different perspectives. The WAP response answers the previous question. While an impartial/scientific explanation is needed for the latter.
Fine-tuning presents the first-person question. Yet, it demands an impartial explanation. It does not reason from a consistent perspective. It effectively assumes we are significant not just to ourselves, but also to the universe. That is why it usually ends up with teleological conclusions. E.g. "I" am the chosen one or, the universe is designed to support life.