Absence of Evidence Is Not Evidence of Absence

Carl Sagan? Martin Rees? William Wright? William Housman? W. J. Sollas? Dugald Bell? Anonymous?

Dear Quote Investigator: The existence or non-existence of intelligent extraterrestrial life is a highly contentious subject. Some thinkers who are open to the possibility of interstellar aliens also believe that the current evidence is inadequate; hence, they advocate using radio telescope dishes as listening devices to collect more data. They also point to the following maxim to discourage premature judgments:

Absence of evidence is not evidence of absence.

This saying has been attributed to cosmologist Martin Rees and astronomer Carl Sagan; however, I think it was circulating before these gentlemen were born. Would you please explore this topic?

Quote Investigator: Tracing this statement is difficult because it has evolved over time. A partial match for six of the eight words occurred in a scholarly paper read during a meeting of the “Victoria Institute” held in London in 1887. The Reverend William Wright’s paper titled “The Empire of the Hittites” argued that data about the movements of the Hittite people was incomplete; therefore, this paucity of evidence should not result in firm conclusions. Boldface added to excerpts by QI: 1

It is urged that the Hittites could not have been settled in Southern Palestine because there are few direct references to their southern settlements in the inscriptions. To this I reply, that the absence of evidence is not evidence. The Egyptians marched up the coast of Syria, and turned inland to Megiddo and Kadesh, where they met the Hittites. The inscriptions are full of the doings of the Hittites at Megiddo and Kadesh, because the Egyptians went thither. They have nothing to say of the Hittites of Hebron, because the Egyptians did not go thither. The inscriptions are records of what happened during campaigns in which Egypt must have made great sacrifices.

Below are additional selected citations in chronological order.

Continue reading Absence of Evidence Is Not Evidence of Absence


  1. 1888, Journal of the Transactions of The Victoria Institute, or Philosophical Society of Great Britain, Volume 21, Ordinary Meeting on January 3, 1887, (Paper read at the meeting by the author), The Empire of the Hittites by the Rev. William Wright, Start Page 55, Quote Page 59, Published by The Victoria Institute, London. (HathiTrust Full View) link