Even if the universe had a cause, why think it is a personal God?

Why the objection is fair

The bare conclusion of the Kalam argument is that the universe has a cause. That alone doesn't tell us much. Plenty of skeptics say the argument, even if sound, gets you a "first cause" that is a long way from the loving Father of Christianity. That's a reasonable point, and defenders need to show their work.

What the cause must be like

The argument's defenders reason from what the cause must be like to explain the effect. If the cause brought space, time and matter into being, it must itself be beyond space, time and matter. So it's timeless (at least without the universe), spaceless, immaterial and enormously powerful. That already rules out most physical mechanisms, since those exist within space and time.

Why personal?

Here is the key step. Suppose the cause were a timeless, unchanging set of conditions, like an impersonal law. If those conditions were sufficient for the universe, the universe would exist as long as they did, which means forever. A timeless cause should produce a timeless effect. But the universe began. How can a timeless cause produce an effect that has a beginning? William Lane Craig argues that the best answer is a personal agent with free will, who can freely choose to create a temporal effect from a timeless state. Water freezes when the temperature drops, but a person can decide to stand up.

A second reason: there are only two kinds of things we know of that are immaterial and could serve as causes: abstract objects, like numbers, and minds. Abstract objects don't cause anything. That leaves mind.

Is this the God of the Bible?

The argument by itself doesn't get you all the way to Christianity, and its defenders don't claim it does. It's part of a cumulative case. Other arguments, like the moral argument, point to a good God. The historical evidence for Jesus's resurrection points to a specific God who has acted in history (see Is Christianity true?). Each argument contributes something.

A fair concession

The step from "cause" to "personal" is philosophically debated. Some find the free-will reasoning compelling; others think we know too little about timeless causation to say.

How to explain this to a friend

With a friend, it often helps to separate the steps. First: does the universe need a cause? Second: what would that cause have to be like? Many people find the step to "personal" surprisingly natural once they see that the cause must be beyond space and time, and that only a free choice explains why a timeless cause would produce something with a beginning. Taking it one step at a time keeps things clear.

The bottom line

A cause beyond space and time that produced a universe with a beginning is best explained as a free, personal agent. That isn't the whole Christian picture, but it's a significant step. For the full argument, see The Kalam cosmological argument.