In an infinite universe, every possible combination of particles will occur an infinite number of times. In this sort of universe, if anything can exist, it must exist. Since a unicorn is a possible combination of particles, somewhere they must exist.
But it gets much more interesting than unicorns. We know that a certain arrangement of particles (your brain) can produce self-consciousness. People are talking of the singularity, when the web becomes self-conscious and grows exponentially intelligent. In an infinite universe, if this singularity event is possible, it is thereby necessary and will have occurred an infinite number of times. Imagine that. An infinite number of exponentially intelligent entities at large in the universe… What if they figure out a way of communicating using quantum entanglement perhaps, or some other process mere humans could never conceive of or comprehend? Suddenly, the idea of universal consciousness begins to look not only plausible, but inevitable. If our web achieves singularity, it would become merely another neuron in a universal brain. We would end up with a sort of scientific pantheism.
But Theists don’t believe God is made from the universe, but rather that the universe exists in the mind of God. “In him we live and move and have our being.” Ok. Let’s grant the existence of a self-conscious, exponentially intelligent life form, say a quantum computer the size of the moon. (In an infinite universe, if that combination of particles is possible, it is necessary.) This staggeringly powerful consciousness would have the ability to simulate a very large number of universes and populate them with mildly intelligent icons like us. We would exist in its mind. If there is one Primary Reality in which our clever computer exists, and a trillion simulations, then statistically we almost certainly exist in one of the simulations.
We once thought the earth was the center. Then it was the sun. Atheists and pantheists still think our reality is the center. Even my talk of quantum computers the size of the moon is geocentric. It assumes the Primary Reality is just like ours, with things in it like moons and quantum particles. But if we are a creation, there may be very little similarity between our reality and Primary Reality. Primary Reality may be very alien and have quite different physical laws. Again, I argue we are not the center. Rather, it is almost certain that exponentially intelligent entities exist, and we almost certainly exist in the mind of one (all?) of them.
And God said, “Let us make Man in our image.”