In 1935, Austrian Physicist Erwin Schrödinger wanted to demonstrate what he thought was the absurdity of the Copenhagen interpretation of quantum mechanics. He meant to establish that matter could not be in two separate states at the same time, a sort of superposition. So he set up a thought experiment.
He imagined placing a cat inside a steel box which could be closed tightly so that nobody could see inside. Also inside the box he placed a small container with a tiny amount of radioactive material with a few atoms. Over the period of an hour, there would be a fifty-fifty chance that one of them might decay and give out a particle. He also included a Geiger counter which he connected to a hammer. If the Geiger counter detected any decay, it would release the hammer, which would break a small bottle of cyanide, which would poison the cat.
Then for the period of one hour, he sealed the box. In that time, we would have no way of knowing if there was any decay, if hammer had been released, and whether or not the cat was dead or alive. The cat was in a superposition state, alive and dead at the exact same time. And only when we opened the door and looked inside, would we know its fate.
At the quantum level though, this is exactly how matter behaves. Our everyday understanding of matter in regard to large-scale objects just doesn't apply with quantum matter. One straightforward example is the electron, which has a spin. It can spin either clockwise, or counterclockwise. Sometimes, an electron hasn't made up its mind yet, and so it's in a superpositioned state where it will spin in either direction. It's only when an experimenter measures the properties of that electron that it will collapse into one state or the other.
So in essence, Schrödinger unveiled a paradox. In a macroscopic system there's no such thing as a partially alive cat. In quantum physics, however, the cat could exist in various states, from completely alive to completely dead, and all stages in-between. However, only one could be observed as 'true' once we opened the box.
Currently, a fierce battle is raging regarding our universe, its design, and a possible designer. While it's increasingly clear that the Universe has pretty much designed itself, there is still the question as to whether or not there's some sort intelligence behind the design: tweaking it, maybe helping it along.
In science, when an idea is put forward, there's a process that then takes place. An observation is made (formal or informal). A hypothesis is proposed. Experiments are designed to test the hypothesis. Depending on the outcomes, revisions are made. Once the experimenter has reached a conclusion, their findings are sent for peer review.
This is a real challenge when it comes to god. At present we have a hypothesis, but all of our evidence anecdotal. God cannot be evaluated. We have yet to figure out how to test it. Attempts have been made, including STEP (Study of the Therapeutic Effect of Intercessory Prayer) but these don't necessarily reflect “god.” So we can neither verify nor falsify it.
That may change. We may, someday, develop the technology and the comprehension to do this, but right now we can't. Einstein, when writing his equations to describe gravity in the universe included a “fudge factor” to put his universe in equilibrium. However, it was proven that the Universe was expanding at a rapid rate, and his “fudge factor” was wrong. He called it his biggest blunder. Only now, we're not so sure. He may have been right after all.
So ultimately, it might be said that god is Schrodinger's Cat. It exists, and does not exist at the exact same time. And until we're able to “open this box,” we simply have to assume that god is in some superpositioned state of both existence and nonexistence at the same time.
Disclaimer: No cats, and no gods were harmed in any way during this thought experiment.