This is the the eighteenth post in my Theories of Knowledge and Reality series. Follow the link for more on the series and for links to other entries as they appear. I've posted an earlier version of this a while ago, but the comments degenerated into a discussion of things completely unrelated to the post. That time, it was a version of my notes on this that hadn't been altered since 2001. I've decided to expand it a bit based on further study of the subject, even though I haven't taught all these issues in the course that this series is based on. I should also say that my presentation depends heavily on William Rowe's work, most importantly the short article he wrote for introductory courses that appears in Reason and Responsibility, ed. Feinberg and Shafer-Landau, with one reference to one other text I have used in that course, Jan Cover and Rudy Garns's Theories of Knowledge and Reality (abbreviated TKR).
The cosmological argument for the existence of God is one of a number of classic arguments sometimes used in conjunction with each other to establish the existence of a being with some of the characteristics generally taken to be true of God. I'm going to look at three such arguments, each contributing something different to the overall picture The cosmological argument in particular occupies a very small role in any overall picture of how some have offered argumentation in support of theism.
The argument relies heavily on the Principle of Sufficient Reason (PSR), which requires an explanation for any actual thing or any fact. William Rowe's criticism of the argument amounts to saying that we have no reason to believe PSR. I will save this discussion for the end. For now, let's take it to be a reasonable principle (if for no other reason than to see what follows).
Given PSR, there are two kinds of things -- dependent things and self-existent things. Dependent beings would be just about anything you come across in ordinary experience and lots more -- rocks, trees, houses, people, stars, electrons, etc. For something to be a self-existent being, its own nature has to provide the explanation for why it exists. God has traditionally been offered as a good candidate for a self-existent being, since traditional theology has always taken God to be necessary and self-existent.
The argument first shows that it cannot be that there are just dependent things, even if they go infinitely back into the past. Thomas Aquinas, Samuel Clarke, G.W. Leibniz, and others who endorse this argument will be perfectly happy to concede (for the sake of argument) that dependent things have always existed, with no beginning, with each explained by earlier dependent things. Aquinas actually doesn't think this could be true, and he gives three very interesting arguments why, but I'm not going to worry about it, because I think the argument can go through even if he's wrong on all those points. So suppose there's an infinite series of dependent things, each explained in terms of a previous dependent thing, with no first dependent thing. Does that explain everything? Some philosophers have thought that it does, since only dependent things exist, and each dependent thing is explained in terms of a previous one.
But this is too fast. Aquinas, Clarke, and Leibniz point out a problem with that conclusion. They can still ask why there are any dependent things at all. Explaining each thing explains each thing but not why there are any at all. The existence of dependent things is still unexplained. This infinite series into the past does not answer that question, which leaves us having to offer another solution -- there must be something that is not dependent, and that thing can provide the answer to the question why there are any dependent things. If PSR is true, then this is in fact the only kind of answer that would do the trick.
Here is a valid argument that reflects this kind of reasoning:
(1) everything is either dependent or self-existent
(2) not everything can be a dependent thing
therefore, (3) there is some self-existent thing
If PSR is true, then (1) is true, because the only other possibility would be for something to be without explanation, and PSR rules that out. Similarly, if PSR is true, (2) is true, since there is no way to explain why there are dependent things by simply adding more dependent things. Some other kind of thing needs to exist, and the only other kind of thing is a self-existent thing. The conclusion logically follows.
A number of objections have been raised against this argument. I will discuss the two that I think are the best in the next post. Some claim that the universe itself is the best candidate for the self-existent thing, and some resist the argument by denying PSR. Comments related to those issues will be ignored. Please save them for the next post in the series. Comments on other elements of this argument are welcome.