This is a "proof" of the existence of God made popular by William Lane Craig and adopted by giddy theists everywhere. It has the appearance of simplicity and, to the casual reader or listener. may even look convincing.
The reality is that the argument's "simplicity" comes from being fast and loose with the precise meanings of words and making a number of unfounded assumptions. The argument, as put forward by Craig, is actually in two parts.
Part 1 - Demonstrating that the Universe has a cause.
1. Whatever begins to exist has a cause.
2. The Universe began to exist.
3. The Universe has a cause.
Part 2 - Defining that cause as God.
1. The universe has a cause;
2. If the universe has a cause, then an uncaused, personal Creator of the universe exists, who sans the universe is beginningless, changeless, immaterial, timeless, spaceless and enormously powerful;
An uncaused, personal Creator of the universe exists, who sans the universe is beginningless, changeless, immaterial, timeless, spaceless and enormously powerful.
There are so many issues with this argument that it's difficult to know where to begin.
Let's look at the argument a bit closer.
1. Whatever begins to exist has a cause. - Says who? In order to make such a statement you must have perfect knowledge of everything that has ever begun to exist or that ever will begin to exist.
While we're at it, define "begins to exist?" When does a table "begin to exist?" After the carpenter finishes building it? When the carpenter starts building it? When the wood arrives from the lumber yard? When the wood is cut at the lumber yard? When the tree from which the lumber is made is cut down or when the tree from which the lumber is made is planted?
Then you can define "cause." Are we speaking about a material cause? An efficient cause? Both? Sticking with the table analogy, the material cause would be the wood; the efficient cause would be the agent of change or the carpenter.
If you say that "cause" here only refers to a material cause then you are admitting that no efficient cause or agent of change is required. If you say "cause" refers to either an efficient cause or both then you are effectively assuming the conclusion in the first premise.
2. The universe began to exist - Again, says who? The mathematics of General Relativity that is used to wind the universe backward no longer works beyond when the universe is a Planck Time old (about 1x10-43 seconds). So no one can say anything about the universe prior to then. We don't know whether it existed or not.
The "Big Bang" simply marks the beginning of the expansion of the universe. No one knows anything about anything prior to that including whether the universe existed or not.
Given that neither premise is necessarily true, the conclusion that the universe had a cause is not necessarily true.
However even if you accept the premises and conclusion, the remainder of the argument that this "cause" should be "changeless, immaterial, timeless, spaceless and enormously powerful" and be a "personal creator" doesn't follow. These are simply a pair of unjustified assertions. An unsupported leap to the desired conclusion.
Even if there was a cause for the universe, this is no reason to conclude that this "cause" was intelligent or even that it survived the creation of the universe.
So, there really is no reason to be impressed with the Kalam Cosmological Argument. I'm not sure if Craig really believes this crap or if he knows it's nonsense but hopes his audience won't recognize it as such.