In presenting the Cosmological Arguments up until now, I've shown them in a positive light, introducing objections only where they are needed to bring on further refinements. This page considers the main criticisms of the Cosmological Arguments- but for a detailed criticism, read the page on the ideas of David Hume and Immanuel Kant.

Debates about infinite regress

Infinite regress is the idea of a process going back into the past with no beginning. Several versions of the Cosmological Argument (Motion and Causality) make it one of their premises that infinite regress is impossible.

But is it?
Infinite regress is certainly unimaginable - we can't imagine something existing forever with no beginning. However, God is also unimaginable. Just because something can't be imagined doesn't mean it's impossible.
The idea of an infinite set of things (an "actual infinity") produces absurd conclusions. William Lane Craig imagines a library with an infinite number of red books and an infinite number of black books. Each black book is a copy of a red book, except for its cover. This means that there are as many red books as black books. It also means there are as many red-and-black books as there are red books - which is contradictory paradox. Craig concludes that actual infinities can't exist in reality.
One problem for religious believers like Craig is that, although an actual infinity is supposed to be impossible, God is supposed to be infinite and possess infinite characteristics - infinitely powerful, infinitely wise, infinitely loving, etc.
Another argument tries to show that actual infinities are paradoxical by showing that actual infinity cannot be traversed (crossed). For example, if you set of on an infinite journey, you would never get to your destination. If you tried to count to infinity, you would never get there. In the same way, if the past is actually infinite, the present would never have happened, because an infinite amount of time must have passed - this is traversing an actual infinity, which is impossible. Therefore, the past cannot be infinite.

William Lane Craig admits that there could be things that are potentially (not actually) infinite. A potential infinity exists when something can be added to indefinitely, without end. So if the universe has a beginning point, it's possible for it to carry on existing for an infinite amount of time "into the future". We wouldn't have to traverse an infinite amount of time to find ourselves living in the present: the past is finite, the future is potentially infinite.
J. L. Mackie suggests this argument shows a misunderstanding of infinite time (he calls it a "prejudice against the actual infinite"). It assumes an infinitely long-ago starting point for the universe which it would be impossible to traverse to arrive at the present. Mackie argues that, in an infinite past, there would be no starting point at all, not even an infinitely distant one. So from any specific point in past time. there is only a finite period of time that needs to be traversed to reach the present.

However, other philosophers argue it is Mackie who is misunderstanding infinity - and that a beginning-less infinite period of time is even more paradoxical than a beginning that took place an infinitely long time ago.
This just goes to show that even philosophers get confused thinking about infinity. It certainly looks as if one side or another - supporters of the Cosmological Argument or its critics - is failing to understand the true meaning of "infinity". But it's hard to tell which...
The PSR does not consider infinite regression. Whether the universe is infinitely old or has a definite beginning makes no difference to this argument. The PSR claims the whole universe requires a sufficient explanation, whether it is infinite or finite.
The KCA also avoids the problem of infinite regress. Philosophers can continue to debate about whether an infinite series is a logical impossibility, but the KCA declares it to be an actual impossibility. This means that, even if an infinite series could exist, the Kalam argument assumes that the universe has a beginning and isn't infinitely old. For hundreds of years, the Kalam scholars had nothing to back this assumption up except religious scripture (revelation from God that the universe was created and was not infinitely old). In the 20th century, the Big Bang Theory put the KCA back in the spotlight, suggesting that its weird and quirky premise that the universe had a beginning was in fact true!
I like to think of Kalam as the Cinderella of cosmological arguments. Her premise that the universe had a beginning seemed so silly for centuries and it had no evidence in its favour except the Genesis story in the Bible. Then, along comes the Big Bang Theory, like a Fairy Godmother, and turns the Kalam argument into a princess.

I suppose that means William Lane Craig is like Buttons - he's made a career out of 'rediscovering' the KCA.
SUMMARY TABLE