Ok, but the thing is that if you don't presuppose humans to be special than the idea of a fine-tuned world loses meaning if other kinds of life-forms could have surfaced instead given different conditions. The other explanation, though, that humans just happen to be what came to thrive under these conditions, and are thus molded by these very conditions, remains very much plausible.
So for this kind of argument to work you have start out by supposing "humans are special". By doing so the conclusion you reach is "the world is fine-tuned for humans", and then one might try to say, from this, that the universe was thus designed to nurture us, since there's this fine-tuning. But this is the same as saying "if humans are special than humans are special".
The bolded part though shows all that could actually try to be inferred about from this: consistency (or negation). As in, supposing it's right won't bring about a logical contradiction or contradiction with the evidence on this given aspect. It could never, however, in any way, be used to try and prove that intelligent design is right, which is what he initially implied (or at least I understood it this way), because the argument would essentially end up begging the question.
Do notice taht saying "humans are not special thus there's no fine-tuning" faces the same adversity. So, focusing only on this very specific arguemnt, both remain equally sound but unprovable. But so is also the case with the idea that the world is fine0tuned for ants or bacteria or whatever. Faced with both possibilities the simpler one seems to me to be the one that involves less "special cases", ie, the one that says the existing species are just a product of their enviroment's condition, and thus "fine-tuned" to it.
As a side note, one might argue the world is not quite as perfect for us as it might be.
I am making an effort to understand, after reading your post a few times, because I'm not a professional in proof and logic.
@underlined. Given the conditions being what they are and not different, then it's more safe to assume that it was indeed fine-tuned for the living organisms we see today. Otherwise, it would be like saying, in a crime scene, that the killer could have used a knife instead of a gun if in other conditions he could only find a knife. If he used a gun, then he didn't use a knife. The fact that he may have used a knife doesn't change the fact that he used a gun. So the conditions in the universe may have been different, but what we are certain of is that they are not different, they are what they are and that's the bottom line. That's what we go by, the actual state of the universe, not what could have been.
@italics. The idea is not to prove than humans are special, but when the parameters required for human existence are very precise it's enough to wonder if it was designed that way. There's not more to this. It becomes an even more nagging question if you see no truth to evolution and naturalistic explanations to life.
Im quite a bit drunk right now, so instead of answering your points directly, I'll try and weave an analogy. Sorry for any incovenience.
See, say you, as well as a million other guys, bet numbers on the lotto. And, for simplicity's sake, say none of you bet the same numbers and that the probability of one of you guys actually getting the numbers right was considerable, statistically speaking.
Now say you actually win the lotto. As in, the numbers drawn are the same as the ones you had bet on.
There are two ways you could see this:
1 - The numbers were drawn equal to mine because I'm special. The numbers drawn are determined by the numers I bet.
2 - I won because I happened to have the right numbers. Other sequencies of numbers had the same probability of being drawn, and in such case some other guy might have won. None of us is special, and who does end up wining is determined by the numbers drawn.
Whenever someone wins such raffle it might seem to them they're in some special position, but that's true despite who exactly wins. So if it's plausible taht on another draw someone else might win, then there's no reason to suppose that any one of these guys is in any special condition.
The point being that the fact that one given guy own - in our example you,you lucky bastard! - can only be seen as saying something about the fairness of the draw itself IF we suppose the very competition would rather have this guy, you, win.
If, on the other hand, the competition was fair, and thus favoured no one, the fact that you won just means you happened to get the right numbers. The numbers could have been different and then any other guys would have won, if not on the first draw then on a subsequent one. You own because your numbers just so happened to line with the drawn numbers, instead of the numbers having been drawn so that you would win. And this isn't at all strange: it's expected that someones umbers would do so eventually.
So the only reason to believe the numbers drawns were so drawn to reflect the numbers you bet on - the only reason to believe the draw wasn't fair with the other competititors - is to believe, beforehand, that the competition favorus you.
Point being that you can't try to used the fact that you've won as evidence that the competition favours you: you winning is evidence of some unfairness if and only if you suppose the competition to favour you. So saying "the competition favours me" and saying "since I won, these numbers must have been drawn because I bet on them" boils down to the same exact same thing, and thus saying "if I won than the competition must have favoured me, because I'm special" is begging the question: you are supposing for starters that you are special among the other competitors. But being special means the competition favours you. So all you are saying is "If the competition favours me than the competition favours me", and that doesn't really add much to anything.
I think I may have gotten a bit less clear than I wanted at the end there, sorry for that. I suppose I don't need to explain how the analogy relates to the topic, but anyway:
The people playing are possible forms of life that could emerge. The numbers being drawn are the characteristics of the many possible worlds, each draw being a world. The competition itself is the universe in the broader sense, and the people fiddling with it, if it is indeed being fiddled with, would be equivalent to "the creator". You represent the human species, of course.
I just hope you can follow this drunken detour of mine and actually take something out of it.