To what extent or in what circumstance is "absence of evidence" considered "evidence of absence"?

For example this question asks whether there's evidence to disprove the idea that fasting is healthy: but what I find is no obvious evidence to support the idea.

On a related note, some people assert in their answers or comments that 'extraordinary claims demand extraordinary proof'.

1 Answer 1


If a problem has been examined by several angles, by various studies, and no clear link has been found, then I think it's not too unreasonable to say that there is evidence of absence.

In those instance, a good answer would look at each (or the most important, if there are too many) and list their findings and their flaws. After a few ones, you'll have made it clear that no study have found the presence of something that they should detect if the claim was true (e.g., correlation between X and cancer), so there is evidence of absence.

If you find literally no study on the subject (which seems what you are saying here), then just say that "To the best of my knowledge, that question has never been examined." in a comment and move on.

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