Full Idea
Two well know slogans (popularised by Carl Sagan) are 'absence of evidence is not evidence of absence', ...and 'extraordinary claims require extraordinary evidence'.
Gist of Idea
Absence of evidence proves nothing, and weird claims need special evidence
Source
Timothy McGrew (Evidence [2011], 'Absence')
Book Reference
'Routledge Companion to Epistemology', ed/tr. Bernecker,S/Pritchard,D [Routledge 2014], p.64
A Reaction
[Sagan was a popular science writer and broadcaster] The second one is something like Hume's argument against miracles. The old problem of the 'missing link' for human evolution embodied the first idea.
Related Idea
Idea 2229 To establish a miracle the falseness of the evidence must be a greater miracle than the claimed miraculous event [Hume]