(“Smoking Gun”)
This fallacy occurs when someone rejects overwhelming circumstantial evidence because of the lack of a single “smoking gun” or specific proof (one that may or may not exist ) and thus declares an entire argument, belief, or position invalid. This is a very common tactic for “denialists,” individuals who deny evidence because the truth contradicts their worldview (usually with the help of a lot of cognitive dissonance). This fallacy is also related to the “Moving the Goalposts” fallacy in which the determination of whether or not the evidence is “good enough” continues to move. This fallacy is seen frequently among global warming denialists, “Birthers,” moon-landing denialists, anti-vaxers, AIDS denialists, holocaust denialists, and creationists.
There is really only one area in which the lack of a single proof bears any weight, and that’s in the field of mathematics. Almost every other evidence-based field accepts evidence from multiple lines, including those that provide both direct and indirect evidence. This is seen perhaps most popularly in the field of forensic science in which clues left behind, though often circumstantial, can lead to clear conclusions. Committing the one single proof fallacy in forensics would be similar to rejecting the suspect’s blood at the crime scene and fingerprints on the weapon, gun powder residue and the victim’s blood on the suspect caught fleeing the crime scene, a known motive, no alibi, and video records of the individual arriving with the murder weapon precisely in time to commit the murder merely because you don’t actually have record of the suspect committing the murder on video tape.
Examples:
Holocaust Gas Chamber Denial: “For four years I have expressed the wish to debate publicly, with anyone whom the other side may care to name, “the problem of the gas chambers”. I am answered with court writs. But the witchcraft trials, like the witch-hunts, never proved anything. I know of a way to move the debate forward. Instead of repeating ad nauseam that there exists an overabundance of evidence to prove the existence of the “gas chambers” (let us be reminded of what this supposed overabundance was worth for the former Reich’s — mythical — “gas chambers”), I suggest, in order to begin at the beginning, that my adversaries provide me with a proof, one single clear-cut proof of the actual existence of a “gas chamber”, of a single “gas chamber”. Then we shall examine that “proof” together, in public.” (robertfaurisson.blogspot.com)
Holocaust denial: “Until I see an actual written order from Adolf Hitler ordering the extermination of the Jews, I won’t believe that it actually happened” (ignoring the fact that Hitler’s hatred for Jews was well-known).
The International Flat Earth Society, an extreme version of Biblical-literalism, rejects the idea that the earth is an oblate spheroid in favor of a literal interpretation of the Bible that includes references to “edges” of an immovable earth. They believe any images taken of the earth are doctored.
Global Warming denialists take several different angles on this as they reject the thousands of peer-reviewed studies that indicate that human-caused global warming is occurring. This particular group also use several other fallacies including the straw man fallacy (misrepresenting the global warming evidence and then dismissing it) and the burden of proof fallacy (Roy Spencer: “Show me one peer-reviewed paper that has ruled out natural, internal climate cycles as the cause of most of the recent warming in the thermometer record.” – You can’t logically prove a negative).
US tax protestors frequently demand that the government show them the specific law that authorizes the income tax while denying the 16th Amendment and Title 26 (the Federal tax code), stating that they aren’t good enough evidence.
“Until I see a death certificate of someone that states the cause of death is exposure to secondhand smoke, I refuse to believe that it can be harmful.”
Anti-vaxers commit this fallacy frequently in their demands for a single study that compares vaxed with unvaxed mortality rates (even though such a study would never receive approval on ethical grounds). They also commit it when they want a single study that shows that all vaccines are 100% safe and 100% effective (ignoring the fact that demanding 100% safety and effectiveness from any medical intervention is impossible and that they should then reject all medical treatment and intervention).
Creationists frequently commit this fallacy when they demand their version of a “transitional fossil” (like a “crock-a-duck”) even though evolution would never predict the existence of such a being. Instead of rejecting all of the millions of real transitional fossils we do have, they hold-out for a single misconstrued idea of what a transitional fossil is supposed to look like and thus reject evolution as a whole based on those grounds.