Revising the Sagan standard

What might really lead us to discover aliens is very ordinary evidence and an extraordinary but strong explanation, one that is hard to vary but fits all the evidence and is consistent with our other theories and observations on how reality works. In fact, I think we should revise the Sagan Standard entirely if we are to get to a new paradigm in astrobiology. In this new paradigm, we should be able to concretely talk about the possibilities for alien life in a rigorous, hypothesis driven and testable way. It is not that extraordinary claims require extraordinary evidence as Sagan put it. But instead we need to recognise that extraordinary claims require extraordinary explanations. The actual empirical evidence can be quite simple. What matters is how the evidence is connected to an underlying explanatory framework and how this interconnects to many of our other observations of our physical world. Scientific revolutions and paradigm shifts are driven by new explanations, not necessarily new evidence.

– Sara Imari Walker in Life As No One Knows It (emphasis added).