From: W. L. Craig: “Professor Mackie and the Kalām Cosmological Argument,” in: Religious Studies, No. 20 (1985),  p. 367.

The kalām cosmological argument, as opposed to the Thomistic and Leibnizian, is one of the better-respected arguments for the existence of God. Because its validity is not controversial, because it aligns with the most prominent scientific theories of the universe, and because it agrees with general philosophical insight concerning properties of infinities, it is one of the more interesting pieces of religious philosophy. It can be stated as follows:

(1) Whatever begins to exist has a cause of existence.
(2) The universe began to exist.
                (2.1) Argument based on the impossibility of an actual infinite:
                                (2.11) An actual infinite cannot exist.
                                (2.12) An infinite temporal regress of events is an actual infinite.
                                (2.13) Therefore, an infinite temporal regress of events is an actual infinite.
                (2.2) Argument based on the impossibility of the formation of an actual infinite by successive addition:
                                (2.21) A collection formed by successive addition cannot be actually infinite.
                                (2.22) The temporal series of past events is a collection formed by successive addition.
                                (2.23) Therefore, the temporal series of past events cannot be actually infinite.
(3) Therefore, the universe has a cause of its existence.