The existence of a deity can neither be disproven nor proven and either stance requires going "beyond" reason.
I am not sure that is fair. While it cannot be proved either way...a deity, after all, seems like a rather improbable thing even if its existence cannot be completely ruled out. I mean one might argue that there is a small teapot orbiting the sun somewhere far out at the edge of the solar system, further than we can detect with any instruments. However, a person might say that this orbiting teapot idea is rather unlikley and might be considered a "reasonable" person for not believing in it (the person has not gone "beyond reason" in this example).
The fact you can't prove or disprove "something" does not make that "something" equally probable to exist or not exist. Evidence, reproducable observations, measurements are the kind of things used to "weight" the probabilties. For example, stepping in front of a high speed car is likely to get you killed or badly injured...again this can't be proved with absolute certainty because there is no guarentee that the world, as we know it, will remain consistent from one moment to the next (we might all live in a fake "Matrix" world for example, and not know it)....but most people accept that it is so highly probable that they are careful not to step in front of a high speed vehicle.