While in discussion with A. C. Grayling on the March 25 edition of the Unbelievable radio program, Peter S. Williams provided a nice, concise presentation of the cosmological argument from contingency:
Once you’ve made the distinction between things that have causes and…things that don’t have causes, if something exists it either is the kind of thing that requires something outside of itself to exist, or it’s not. If it’s not possible for there to be an infinite regress of things that do require causes outside of themselves, and it is true that something exists which does require a cause outside itself [the universe, and everything in it]…,there can’t be an infinite regress of such causes, and therefore you have to have a termination of that regress. [God is the best explanation for the termination of that regress.]
For those of you for whom this to be a bit too concise, let me flesh it out a bit.