Yeah, my bad. I read your op a long time ago (the night you first posted it) then started mulling over the paper. I forgot that you mentioned you specifically want to discuss those four particular arguments. I don't think those four arguments are the real crux of their case, but I am happy to discuss them nonetheless.
Let me just say something quickly about the my "free will argument." I accept the characterization so long as we clarify it is a type of free will defense. It isn't the same as the free will defense. I am aware that the free will theodicy is controversial, in fact, I don't accept it. What I am doing here is stealing a single maneuver used in that argument and applying it to this issue. My argument will succeed or fail on its own merits.
What difference does(or would) God of Classical Theism make in the world? Why would one want him to exist? (it important for theist that God's existence actually does make a difference in the world because then he might be able to offer pragmatic reasons for inferring God's existence where for example a premise of a Cosmological argument is dubious, or generally its the very point of accepting theism..)
Okay, fair enough. That isn't my preferred way of arguing theism, but pragmatic arguments are useful regardless, and I do think there are pragmatic reasons to accept theism, including ones that have to do with the meaning of life.
First off, it seems obvious to me that one doesn't need to hold a strictly theistic account of the meaning of life to affirm that the existence of God adds something valuable to one's account. For example, in the account I offered, one could have a meaningful life even if God doesn't exist so long as one lives for a purpose that has intrinsic value. However, if God exists then we have reason to believe we were made for an ultimate purpose (whatever it is). Such a purpose would be extremely valuable and affirming to our intrinsic worth. So while meaning is possible in an atheistic world, there is a higher ceiling for potential meaning under classical theism. That is one advantage theism has.
Anyways, let me say something now about the four arguments you wanted to discuss:
Argument One: The authors admit that this argument is undone if one distinguishes between purposes we chose for ourselves and the purpose for which God made us. They write in the conclusion: "For instance, maybe God created us for some purpose, and our lives have ultimate significance only insofar as we fulfill this purpose" (which is what my account does). They then move on to argument two to demonstrate this cannot be, so argument one isn't relevant where my account is concerned.
Argument Two: This is the most important argument for me since the authors clearly frame it as an argument against the proposition I quoted above, namely "That God created us for some purpose, and our lives have ultimate significance only insofar as we fulfill that purpose." Let's call this the Ultimate Purpose claim (UP). I agree with UP, depending on how we are meant to interpret it, and I think their arguments against UP fail (I take them to be offering two avenues of argumentation for the same conclusion in the section titled "Argument Two".
The first argument I would summarize as follows:
(1) Supposing human life has meaning, it is either intrinsic meaning or extrinsic meaning
(2) If intrinsic, then UP is false, because we would have meaning regardless of the purpose God creates for us.
But then suppose that meaning is extrinsic in that meaning is only found in some relation to God. In that case:
(3) God's existence is sufficient for life to have meaning.
(4) If God's existence is sufficient for life to have meaning, then all life will have meaning.
(5) If all life has meaning, then meaning doesn't depend on the nature or content of a life.
(6) Meaning (probably) does depend on the nature or content of a life.
(7) Therefore, meaning (probably) is not dependent on some relation to God.
As you have probably already guessed, I would just reject (3) on the grounds I have already outlined in my other posts. This is just more evidence that the proposition "If God exists, then all lives have meaning" is really the crux of the entire paper, which is why I thought it was sufficient to simply discuss it.
Nonetheless, there is another part of the above argument that confuses me. UP is a claim about ultimate significance/meaning, not about meaning in general. A theist can accept (as I do) that meaning in general is possible without God but maintain that there is a higher dimension of meaningfulness, ie. ultimate meaning, that still depends on the existence of God. I think this is enough to justify the intuition that most of us have that a world without God would lose something important as concerns meaning in life. Perhaps when Megill and Linford used the phrase "ultimate significance" they didn't mean it in the same way I understood it. Perhaps they meant something life "true meaning" or "actual meaning," ie. general meaning that exists. If that is the case I don't see why a theist would be motivated to accept UP.
On page 14 they begin another argument against UP where they outline the four possible positions one could take concerning the purpose and meaning we ascribe to ourselves in relation to the purpose and meaning God ascribes to us and argue that each is problematic, suggesting that God is not necessary for life to have meaning. I am willing to grant that the second and third positions (b and c) are indeed problematic. I think their problems with (a) and (d) are weak. For the sake of space, I am just going to discuss (a), because I think it is the most important. Notice their argument depends on them showing that all four positions are problematic, so if I can show that even one of them is tenable I will have done enough to cast doubt on the whole argument.
Concerning position (a) the author's say the following:
First, Suppose that (a) the purpose we devote ourselves to matches the purpose for which God created us. But it is not clear that simply following God's purpose for us would be sufficient to imbue life with meaning. For example, even though a child might be created by her parents for some particular purpose, the child might have no obligation to fulfill this purpose. If Sue learns her parents created her solely for the purpose of harvesting her organs for a sibling, Sue has no obligation to fulfill this purpose. There are many differences between God and human parents, and perhaps there is some relevant difference in virtue of which God's purposes for us should be our purposes for ourselves, but it is difficult to see what that relevant difference could be. (14)
To me, the relevant difference is obvious: human parents are creators of an instance of a particular form, God is the creator of the form itself. Imagine there was a task you needed to perform and you invent the perfect tool do it. The tool is so perfect that you make several molds for other people to make their own. Now imagine I got a hold of a mold, made the tool, but then used it for some other task, one completely different than the one you designed it for. Should I expect the tool to be perfect for my task just because I made it? Obviously not. If God exists he would be the designer of the human form and could fashion it to be perfect for the end he desired. Such an end would be proper to our very essence and thus be fulfilling to a degree that is impossible in a world without God. What is more, in classical theism God is not just some being who is good, he is goodness itself. If it isn't meaningful to pursue the purpose that the Good itself designed you to pursue specifically then I don't know what is.
So thats arguments one and two. Let me know what you think.