The kalam cosmological argument for the existence of God originated and became highly developed in Islamic theology during the late Middle Ages. It gets its name from the word "kalam", which refers to Arabic philosophy or theology. Traditionally the argument was used to demonstrate the impossibility of an actual infinite existing in the real world, as well as an argument from temporal regress, thus showing that the universe cannot be eternal. In recent years these philosophical arguments have been confirmed by scientific discoveries, viz., the Big Bang theory. The most thorough and articulate proponent of the argument today is Dr. William Lane Craig.
Statement of the (modern) deductive Kalam Cosmological Argument:
p1. Everything that begins to exist has a cause of its existence. (Causal principle.)
p2. The universe (space, time, and matter) began to exist. (Evidenced by two philosophical arguments, the Big Bang, and the second law of thermodynamics.)
c3. Therefore, the universe has a cause of its existence.
sp1. As the cause of the universe (space, time, and matter), the cause must be outside of space, time and matter, and therefore be spaceless, timeless, and immaterial. Moreover, the cause must be a personal agent, otherwise a timeless cause could not give rise to a temporal effect like the universe. (Argument expanded.)
sp2. This is an accurate picture of God.
sc3. Therefore, God exists.