Instead, I found myself responding to not to just a couple of counterpoints, but to a number of arguments multiplying so fast that I couldn't possibly keep up. I'd attack the first six, and not only would I not have convinced my opponents, but there would suddenly be six more arguments on top. If I attacked those, there would be six more. No arguments were ever conceded, either, so they could cheerfully go right back to the first six arguments if they ever ran out of new ones. This is a not a new insight -- people have compared arguing with certain people to playing Whac-a-mole.
I was thinking about how frustrating this situation is, though, and I realized that not all of the arguments are equally important. Some arguments reflect the genuine reasons the person believes in their position, while others are arguments they just think will help their case. I'd like to call these load-bearing arguments and cosmetic arguments.
Load-bearing argumentsThese are the only arguments that matter. If you can convince someone that a load-bearing argument is false, then it will rock their belief. It won't necessarily convince them, because if their belief is psychologically important to them, they'll quickly shove a bunch of other arguments under there and hope they hold, but you're not wasting your time. If you could convince them that the load-bearing argument is false, it's going to at least temporarily shake their confidence.
Cosmetic ArgumentsThese arguments are just for show. They exist to create the appearance that the belief is supported by a vast and ever-multiplying array of arguments, but they are just decoys. Upon examination, not only do they not hold up, but you realize even this particular believer isn't convinced by them.
It's important to realize that an argument is load-bearing or cosmetic for a particular person -- it's not an objective categorization. One person's load-bearing argument might be another's cosmetic one and vice-versa. There are some arguments, though, that are always cosmetic.
Some examplesLet's take abortion. I think "God says it's wrong" is a load-bearing argument. If (obviously a big "if") you could convince a person who uses this argument either that God does not exist or that He does not say it's wrong, it would shake their belief. Again, it's possible that they would hold onto it by putting other arguments under it, but there would have been a moment when the belief was actually at risk.
"Abortion is murder," on the other hand, is a cosmetic argument for most people. If you could convince someone who says this that abortion and murder aren't exactly the same, they would likely still oppose abortion without ever wavering. That's because they don't really believe this argument in the first place -- their belief rests on a different argument entirely. (As evidence that they don't really believe abortion is murder, they would send a woman who killed a baby to jail, but would never send a woman who has an abortion to jail.)
How about our old favorite, the existence of God. I think some version of the Argument from Design is often a load-bearing argument. I'm not talking about the formal argument -- I don't think formal arguments are good representations of how people actually think -- but the genuine intuition that some intelligent being must be responsible for the dazzling complexity of the universe. If you can convince a believer that the universe *could* have come about without a designer, you will often have genuinely shaken their belief. Again, they might not be convinced, they can shove other arguments under their belief, but there will be that moment of panic. I think that's what happened to my belief in God. Hawking shook it with A Brief History of Time and Dawkins sealed the deal with The Blind Watchmaker.
That's why Darwin was so revolutionary and why he is still so reviled by many religious people -- he didn't just disprove a literal reading of Genesis, he demolished the Argument from Design as it applies to biology and human beings. Even though he didn't explain why the universe exists, how the planets formed, or even how life began, it was enough of a blow to the idea of a Designer that it convinced a lot of people, himself (probably?) included, that God does not exist.
Note that the Argument from Design is not load-bearing for all believers. Some believe that they have personally witnessed God or that they can see him in everyday life. For them, the Argument from Design is a cosmetic argument and this other thing is the load-bearing one. Convince them that the universe could have come about without God and it won't shake them. But if (huge if) you could convince them that what they experienced was a hallucination, for example, or that what they took to be God's influence was really a series of coincidences, then their belief would be rocked.
I think the Ontological Argument is a rare argument that is *always* cosmetic in all its forms:
When we hear the words "that than which a greater cannot be thought", we understand what the words convey, and what we understand exists in our thoughts. This then exists either only in our thoughts or both in thought and reality. But it cannot exist only in our thoughts, because if it existed only in our thoughts, then we could think of something greater than it, since we could think of something than which a greater cannot be thought that exists both in thought and in reality, and it is a contradiction to suppose we could think of something greater than that than which nothing greater can be thought. Hence, that than which a greater cannot be thought exists both in thought and in reality. Therefore, that than which a greater cannot be thought really does exist, and in later chapters of the Proslogion Anselm argues that this being has the traditional attributes of God like being the omnipotent creator.
I can't imagine anybody's belief rests on such an obvious gimmick.
How to Tell the DifferenceAgain, most arguments can be either load-bearing or cosmetic, depending on the believer. It's all about the genuine reason the believer believes, and that might be ultimately unknowable. However, I think there are some clues.
Some arguments are clever, and the believer might be proud of them. This is usually an indication that it came after the belief already existed and is used simply to score points -- that's why the believer is proud of it. The Ontological Argument, discussed above, is a prime example.
When I was in yeshiva, we were talking with our rabbi about the "apparent" contradiction between an omniscient God and free will. (In Orthodox Judaism, playing Resolve that Contradiction! is a popular pastime, both in casual conversation and in Torah study.) I came up with an analogy. I said we people living in this century can look back at people living in the last century and know that they chose X instead of Y and yet they still had free will. So, since God exists outside of time, it's pretty much the same thing.
The rabbi was delighted and the other students smiled and nodded and I was really proud of myself for coming up with such a clever argument. The argument, though, now that I don't believe, is obviously bullshit. Even if we allow for a God that exists "outside of time," he also must be "inside of time," because he allegedly interacted with the universe in the past. Therefore, he knew about people's choices before they made them and the contradiction still stands.
If someone had pointed out the flaw in my argument to me then, I would have shrugged and been like, "Oh yeah, good point" but my underlying belief in God (and free will) wouldn't have been shaken for even an instant. That's what makes it a cosmetic argument.
Oftentimes, a believer will offer up an argument or several tentatively. Now, obviously, there's nothing wrong with offering an argument tentatively rather than confidently, especially if it's a bad one or one not yet investigated or challenged, but it's on obvious indicator that it's not load-bearing. Either the person does not yet believe the conclusion of the argument (hence the tentativeness) or the person already believes the conclusion and the argument is just cosmetic.
For example, in this thread at the great XGH's, commenter Thanbo offers four "solutions" to the same problem - the conflict between the Documentary Hypothesis and the belief that God dictated the Five Books to Moses - and adds "I'm sure there are others I haven't thought of." Clearly, regardless of the merits of the individual arguments, they are all cosmetic because if you knocked them down, it won't affect Thanbo's belief. He's sure there are others.
I find that a lot of believers who think of themselves as more open-minded (but not so open-minded that their brains fall out!) do this. They see a contradiction in their beliefs and are too "open-minded" to either pretend it doesn't exist or to pretend that any particular argument resolves it, so they'll say well this could be a solution or that could be a solution, etc. Ultimately, if you destroy every "solution" they offer, they'll just shrug and concede that it's an issue, but it won't shake their faith in the slightest.
Arguments that don't directly support the belief
Some "arguments" don't really support the belief in question. For example, Pascal's Wager is more of an attempt to convince the audience that it's in their self-interest to believe than it is an argument that the belief in question is true. Arguments that not believing would have adverse effects (religion makes me happy and healthy or it keeps me behaving) might point to explanations for a person's belief, but they aren't load-bearing because knocking them down would not directly affect the person's belief.