The main question the cosmological argument ponders thought on is ‘Why is there a universe at all?’ The cosmological argument asks the scientific question behind the universe as the design argument asks an emotional one.
One of the main strengths of the cosmological argument was brought forward again recently by William Lane Craig. The argument tries to say that the world couldn’t have just occurred, there must be some sufficient reason. Gottfried Leibniz is the most asscoitated with this idea of ‘The principle of sufficient reason’ ,he says that anthing that happens ,including the universe, must have become due to a definite reason. Therefore there must be a course or an explanation. However there comes a point when we no longer need to look for an explanation anymore and therefore that’s when we have a sufficient reason. The cosmological argument says this sufficient reason is God.
Back to William Lane Craig, he brought the idea of the ‘Kalam cosmological arguyment back (however it was first developed by the Muslim Philosophy of Religion). There are 3 main steps to this argument which are
1) Whatever begins to exist is caused to exist by something else
2) The universe began to exist
3) Therefore, the universe has a cause and this cause is God.
Step one of the Kalam argument is just common sense. Step two is also common sense as long as not looked into too deeply, which it’s not needed to be, it’s a Brute Fact as Bertrand Russell may say. Lastly the last step may to a first glance seem to jump majorly and offer a completely inaccurate response but it seems like the simplest answer (e.g. Ockham’s razor) therefore it’s the most ration explanation. Some may argue God needs a cause or an explanation then but God is the Cosmological sufficient reason.
Coplestons argument is very similar to the one of William Lane Craig although the points seem slightly more detailed