Great. So we have this model, and it has some set of constants and parameters, and these constants and parameters have to have very precise values to make the model match reality.

If we accept some very strong form of scientific realism, this is the same as saying that the universe itself probably actually constants and parameters of these values.

So, we ask, either:

A.) Why is the universe such that this model requires such precise values of its constants and parameters to match it, or

B.) Why does the universe have these values for its constants and parameters (related to each other by the form of this particular model)?

The proponent of the fine tuning argument, depending on whether he has taken interpretation A or interpretation B, above, says,

A.) Well, our universe allows for life as we know it, and most universes matched by a model of the same form with different values for its parameters would not.

B.) Our universe allows for life as we know it, while most universes with different values for its constants and parameters (related to each other, again, by the form of this particular model) would not.

The apologist's task, then, is to take one of these two interpretations and show that he can use this fact to exclude or reject all cosmological hypotheses that do not include the universe being designed, or to show that some set of design hypotheses has a higher likelihood for the fact in question (whichever fact you pick, depending on your interpretation) than any competing set of non-design hypotheses.

Unfortunately, none of the apologists who actually pursue this line of reasoning possess even the philosophical sophistication to frame the question in a cogent manner, much less the ability to answer it or perform the task that their argument requires.

Think about the two most prominent FTAs in common usage: Craig's and Collins's.

Craig's relies on the premise "Fine tuning is not due to necessity or chance." However, his justification for this premise relies on the assertion that "the probability of fine tuning on chance is unimaginably low." This, however, is either a lie or a sophomoric error. In fact, Craig has never evaluated this probability at all, and neither has anyone he has quoted. In fact, he has made it clear that he is too deeply ignorant of probability to evaluate this probability even if he wanted to. He doesn't actually even understand what the phrase he has used means.

Collins's argument relies on the premise that "P(LPU|T) > P(LPU|ASU)." However, while Collins is more or less using likelihoods correctly, here, he also has not evaluated these likelihoods and, indeed, clearly does not possess the command of probability theory to actually do so, or, in fact, even a full understanding of what these terms represent.

This is the same critical failure in both cases: the argument rests on a likelihood (the probability of whatever "fine tuning fact" you want to consider given some space of non-design hypotheses, be it "chance" or "ASU") but in both cases that likelihood is not calculated. It is not estimated. In attempting to discuss it, both "philocophers" reveal that, in fact, they have no idea what it is or how it might be calculated at all.

Until some calculation of these conditional probabilities is actually offered, any rational person who actually understands the matter under discussion must reject both arguments. They are both laughable failures, serving only to highlight their author's remarkable lack of philosophical sophistication.