No single person, group or authority. It is an ongoing determination by many people from a host of backgrounds, biases and intentions who still all agree on wha

No single person, group or authority. It is an ongoing determination by many people from a host of backgrounds, biases and intentions who still all agree on what is reasonable and what is not. It is determined by merely asking oneself "do I have doubt that is logical, fair and as unbiased as possible?". Gather enough of these people - from as wide a field as possible - and you have reason.