Absence of evidence is not evidence of absence.

On extraterrestrial life:

Absence of evidence is not evidence of absence.

Quoted in Project Cyclops, edited by B. M. Oliver and J. Billingham (1973)

Martin Rees Quotes

Absence of evidence is not evidence of absence.

Absence of evidence is not evidence of absence.

Absence of evidence is not evidence of absence.

Absence of evidence is not evidence of absence.