At the Secular Outpost, Ryan M posted a reasonable effort at summarizing some of the common mistakes made by non-experts in philosophy of religion. For this discussion, I'd like to focus on the first of those mistakes.
Mistake 1 - [Failing to understand basic cosmological arguments]The first thing I would note is that I'm not sure that this is actually the way many atheists interpret or understand the argument. I don't see it quite that way. And I certainly am aware that there are various formulations of it that don't all follow the same logical flow, but I want to focus on the second way of Aquinas specifically. This is his argument for a first efficient cause of being, and I'll explain it the way I understand it. Quodlibet states the argument this way:
- Many non-experts, presumably all atheists, interpret cosmological arguments in general as having the following form:
1. Everything has a cause.
2. Therefore, the universe has a cause.
3. If the universe has a cause then God exists.
4. Therefore, God exists.
5. If God exists, then God does not have a cause.
6. Therefore, God does not have a cause.
The obvious issue is premise 1. Where can we find a cosmological type argument with a premise like that? Not in Aquinas, not in Duns Scotus, not in Leibniz, not in Aristotle, not in Koons, not in Pruss, not in Craig. Probably, no prominent defender of theism has used such a premise, and it's hard to tell if anyone has used it other than people misinterpreting arguments made by one of the listed philosophers.
1. We see in the world an ordered series of efficient causes.I think this version of the argument follows Aquinas fairly well. Aquinas says that this is an a posteriori argument. That means its premises are established by observation. So with that in mind, it's reasonable to interpret the first two premises as rules of nature based on what is observed. I'd say the rules he establishes are: 1 - that things have causes, and 2 - that the cause of anything is not the thing itself. Aquinas does not explicitly say that everything has a cause, but since he's talking about what we observe, there's no reason on that basis to suppose that this rule shouldn't apply to everything, unless you want to smuggle in some additional unstated assumption (which theists surely do). Actually the notion of an ordered series is elaborated in statement 3a, and it includes a first cause, but that first cause is NOT something that we observe. So it is fair to say that Aquinas does indeed smuggle in an assumption here.
2. No thing can be its own efficient cause,
a. for this would require it to be prior to itself, which is impossible.
3. This series of efficient causes cannot be infinite,
a. for all efficient causes follow an order: first, intermediate, ultimate.
b. if there is no first cause, there can be neither ultimate nor intermediate
i. for to remove the first cause is also to remove its effect
c. in an infinite series there could be no first efficient cause, no ultimate effect, nor any intermediate cause; but this is plainly false.
4. Therefore, a first efficient cause is necessary; which we all call God.
Statement 3 of the argument is supported by its own argument, given in 3a, 3b, and 3c. Statement 3a declares that there must be a first cause before any intermediate or ultimate cause (because that is the order that causes follow, according to Aquinas). Statements 3b and 3c merely reinforce the point that there has to be a first cause in any chain of causation, and that's the basis for concluding that there cannot be an infinite chain, which doesn't have a first cause. This is the way I read Aquinas: he's saying that there cannot be an infinite chain of causation, because there has to be a first cause. And the insistence that there must be a first cause is nothing more than a bald assertion.
And this is problematic, because that assertion is the same as the conclusion of the argument, given in statement 4. Try as hard as I might to see it differently, I cannot help but think that statement 3a begs the question, because the conclusion reached in statement 4 is assumed right there in statement 3a. Begging the Question is a logical fallacy described as:
Any form of argument where the conclusion is assumed in one of the premises. ... Begging the question is a form of circular reasoning. - Logically FallaciousAnd there is an additional problem with this conclusion, because this thing that is regarded as first cause, whether it's God or something else, is assumed to be uncaused. But that is not consistent with the implicit rule established in statement 1 - namely that things have causes. But the first cause doesn't follow that rule. It is the one and only exception. And this might be seen as special pleading, another logical fallacy.
Applying standards, principles, and/or rules to other people or circumstances, while making oneself or certain circumstances exempt from the same critical criteria, without providing adequate justification. Special pleading is often a result of strong emotional beliefs that interfere with reason. - Logically FallaciousNow, I'll admit that there may be good reason for assuming that something exists without a cause, despite Aquinas' claim that this argument is based on observation (and I don't think he was saying that we observe such things). So I'm willing to let Aquinas off the hook for this one. But if this objection is valid (and I don't think it's so unreasonable, because the argument as presented fails to establish the necessity of a first cause, other than simply asserting that there must be a first cause), then there is justification for asking that oh-so-ignorant question: Who made God?
Nevertheless, that brings us to another issue. Why does the first cause have to be God? And why does it have to be just one thing? There is certainly no logical reason given in this argument that would preclude the possibility of one or more first causes that are not God. This thing, whatever it might be, would be known as a brute fact. But for some reason, Aquinas did not see fit to include this logical possibility in his second way. And that's what we call a False Dilemma (or excluded middle).
When only two choices are presented yet more exist, or a spectrum of possible choices exists between two extremes. False dilemmas are usually characterized by “either this or that” language, but can also be characterized by omissions of choices. - Logically FallaciousSo this is the way I understand Aquinas' cosmological argument. I don't claim to be speaking for all atheists. I know there are many people who think that Aquinas' logic is bullet-proof, but I have yet to see any explanation (beyond "Thats just ignorant") that satisfies my objections. I would welcome any cogent explanations that clarify my possible misunderstandings about this argument.