God at the end of the rainbow
God at the end of the rainbow is a theological problem which highlights the limited thinking of people in older religions and the evolution of the home of the gods. As we look further back in history, the dwelling place of gods becomes more mundane. Generally speaking, this problem highlights a moving the goal-posts type fallacy.
Going back around 3,000 years ago to some of the oldest surviving religions, the gods lived in places inaccessible to morals. The ancient Greeks believed their gods lived on Mount Olympus, the ancient Hindus believed their gods lived on Mount Meru, those ancient Hebrews who worshiped Yahweh believed he lived atop Mount Sinai, while those who worshiped Elohim believed he lived atop Mount Horeb. It's not always mountains either: Hapi, one of the Egyptian Nile gods, was believed to live among the many caverns far away at the source of the Nile. Necessity requires the home of the gods to be where mortals can't reach. However, as people began to expand across the land and climb to the tops of mountains, they failed to see any gods, and the idea of gods living on the boring old earth seemed a little childish, so religious beliefs evolved.
Around 2,000 years ago religions claimed their gods lived way up in the clouds where no mortal could ever reach. This is what the early Christians believed, (I Thessalonians 4:17), and, in the Turkish religion of Tengrism, the god Tengri lived in the sky as well. Over time, people invented gliders, hot-air balloons, and other early flying machines, and the idea of gods living in the clouds seemed a little childish, so religious beliefs evolved.
200 years ago, Latter Day Saints and Mormons believed their god lived on a distant planet called Kolob, where no mortal could ever reach. Then, scientists developed powerful telescopes and launched probes to the various planets in our solar system, and landed on the Moon, and the idea of gods living on other planets seemed a little childish, so religious beliefs evolved.
Now, gods don't live on mountains, or in the sky, or even on other planets. Instead, most modern religious believers claim that their gods live in a spirit realm where no living mortal can ever ever go. Each time the home of the gods was in danger of being reached by mortals it was necessary for religious beliefs to evolve and push the home of the gods out just a bit further. Just as you can never get to the end of the rainbow, you can never get to the home of the gods; they're always living just out of reach.