1) Whatever begins to exist has a cause.
2) The universe began to exist.
3) Therefore, the universe has a cause.
This is the logical form of William Lane Craig's Kalam Cosmological Argument for the existence of God. Let's evaluate it.
Formally, it is valid. That is, if premises 1 & 2 are true, the conclusion (3) necessarily follows.
Premise 1 seems to be true. To prove it false one would have to show that there exists at least one thing that came into existence without being caused.
Premise 2 is true, Craig says, for two reasons.
a) The first reason premise 2 is true is that an actual infinite is impossible. Actual infinity is a mathematical concept that can have no applications because it would lead to logical absurdities. See Craig's article "The Existence of God and the Beginning of the Universe" right here.
b) The second reason is that science confirms that our universe began to exist. This is the conclusion, reconfirmed continuously, of cosmology.
But why must the cause be God? The cause of the universe must be God because the cause must be nontemporal (when the universe began to exist time began to exist), nonphysical (when the universe began to exist matter began to exist), extremely powerful, and creative (personal agency). These attributes - nontemporality, nonphysicality, powerful, and creative - cause us to inductively infer that God is the cause of our universe.