The phrase “Extraordinary claims require extraordinary evidence” was popularized by Carl Sagan (1934-1996), a well-known astronomer and author who hosted a TV series called “Cosmos,” published hundreds of scientific articles and was professor of astronomy at Cornell University in New York.
Requiring extraordinary evidence for extraordinary claims sounds good on the surface. But, it is subjective. The fact is that a person’s presuppositions strongly affect how and to what degree the statement is applied. In Jesus’ resurrection, for example, Christians presuppose that God exists and that He could easily have raised Jesus from the dead. The evidence of fulfilled prophecy, eyewitness’ records, and changed lives of the disciples is enough to convince many people who believe in God that Jesus rose from the dead. This is a logical conclusion based on the presupposition and the evidence.
Atheists, on the other hand, would negate the resurrection by default since their presupposition that there is no God would require that God’s involvement cannot occur. Therefore, for an atheist, the extraordinary evidence would have to be “exceptionally” extraordinary in order to overcome his atheistic presuppositions. In other words, evidence would need to be presented that was rock solid and irrefutable.
This is why the skeptic must require “extraordinary evidence.” It enables him to retain his presupposition should the extraordinary level of the evidence not be met. Therefore, requiring extraordinary evidence effectively stacks the deck against the claim.