I just listened to this debate between atheist, ethicist Peter Singer and Christian apologist Dinesh D'Sousa.
First I'd like to say how thoroughly distasteful and un-Christian I have found Dinesh D'Sousa in every one of the debates I've seen of him. He is guilty of the totality of fallacies expounded in any Logic 101 class, his personal favorite obviously being the ad hominem. And his manner is drenched in the arrogance of the epistemological bigot whose faith in their own rightness is unshakable by even the strongest of evidence. Despite my personal dislike of him, I would like to address the misconception that he advances numerous times in this debate, in his attempts to protect his iteration of the so-called "cosmological argument" for the existence of God, about the nature of the current science on cosmology.
The cosmological argument goes something like this:
Premise One: Everything that begins to exist has a cause.
Premise Two: The universe began to exist.
Conclusion: Therefore the universe had a cause. Further, since the universe contains all matter, space and time, the cause of the universe must be non-physical and transcendent, i.e. outside space and time. This non-physical transcendent creator of the universe is a personal God.
Now, there are a number of valid arguments against this. One can say: you cannot assume a characteristic about a set by the fact that all members of the set have that characteristic. Since the universe is a set of things and not a single thing itself you cannot assume one of its characteristics by the characteristics of those things which it contains. As analogy: Every floor in that building is ten feet high, therefore that building is ten feet high.
Another way you can refute the cosmological argument is by denying premise two, that the universe began to exist. This was the most popular argument among atheists for a long time. They would say that the universe has simply existed forever, therefore it cannot have a creator because it was not created. This argument was dealt a blow with the discovery of the cosmic microwave background radiation which clearly showed that the observable universe did indeed have a beginning in the "big bang" some thirteen to fourteen billion years ago. However, I do not believe, as many do, that this blow was fatal. This is because the big bang only describes the beginning of the observable universe. Inflationary cosmology has nothing to say about what occurred at or "before" (if you can use the word before considering that the time of our observable universe itself came into being with matter and space at the big bang) time point 0. The modern cosmological model has nothing to say about whether anything existed antecedent the big bang, it could have been an event of information destruction rather than of creation. It could be that a universe has existed eternally in an alternating pattern of expansion and contraction away from and back into a time point zero singularity which acts as a sort of dividing point between observable universes through which no information can pass.
Or one can posit the existence of a multiverse which eternally spawns offspring bubble universes of which our observable universe is one. There are varying amounts and qualities of evidence for each of these positions, but in my opinion all of them, as naturalistic hypotheses tend to be vastly more probable than any supernaturalistic hypothesis.