Why the Universe Had a Beginning — and Why That Is Still Interesting

Popular apologetics has leaned hard on the standard Big Bang model for half a century. Cosmology has not stood still, and any argument that depends on a model of the 1970s is a hostage to the next paper.

What survives is narrower and more durable.

The theorem and its limits

Borde-Guth-Vilenkin is not a proof of God. It is a reason the question will not go away.

The Borde-Guth-Vilenkin result shows that any spacetime with an average expansion rate greater than zero over its history cannot be extended infinitely into the past. It is a statement about geodesic completeness under a stated condition. It is not a statement that the universe began to exist in the metaphysically loaded sense, and Vilenkin himself has been careful about this.

Proposals that evade it exist — cyclic models, emergent universes, quantum-gravity regimes where classical spacetime fails. Each has costs, and several have empirical problems of their own. None is established.

The philosophical question

Suppose the physics remains open indefinitely. The contingency question does not depend on it. Why is there a universe with these laws rather than none, or others? A model that pushes the boundary back does not answer that; it relocates it.

What not to claim

Do not say science has proved God. It has not, and a reader who later learns otherwise will rightly discount everything else you told him.

Say instead: the universe looks like the kind of thing that has an explanation, and every serious attempt to explain it ends in either a brute fact or a necessary being. That is an argument worth having, and it does not expire with the next preprint.