Trying to prove a negative

John Muenzberg

Column by John Muenzberg, lecturer of philosophy

Last fall, Democratic candidate Hillary Clinton lost the presidential election, but she did receive almost three million more votes than Republican candidate Donald Trump. After the election, then President-elect Donald Trump tweeted that he would have won the popular vote if it had not been for 2-3 million illegal votes cast.

In response, reporters and congressmen asked for the evidence of such cheating. This is understandable, as several million illegal votes would be an unprecedented level of voter fraud. Despite regular allegations of voter fraud, the number of illegal votes cast is usually in the single digits, not in the millions.

The more interesting response came from people who challenged media criticism and asked for evidence that there was not illegal voting. They thought that if nobody can prove that there was not illegal voting, then we should accept that illegal voting did happen.

This type of argument is a fallacy, known as an argument from ignorance. The typical form of an argument from ignorance is to assert that something must be true because there is no evidence proving it to be false. The reason that this is a fallacy is that the argument form can be used to prove either side of an argument.

If you accuse someone of cheating, you might argue that since they cannot prove their innocence, then they are guilty. They in return can argue that since there is no evidence they did cheat, then they did not. The lack of evidence should result in no conclusion being drawn, not evidence for one side or another.

This is why U.S. courts require the prosecutor to prove someone’s guilt in court. Guilt requires positive evidence of guilt, not simply a lack of exculpatory evidence.

But the argument from ignorance is also central to arguments called conspiracy theories. The term is not restricted to actual conspiracies, but also includes complex arguments with only circumstantial evidence. Such arguments have a peculiar status because the lack of concrete evidence actually makes them harder to deny.

On Dec. 4, 2016, Edgar Welch entered a pizza restaurant in Washington, reportedly to investigate a supposed child sex ring run out of the location. Edgar Welch is alleged to have fired three shots from a rifle, although nobody was hurt.

Welch became convinced the pizza restaurant was engaging in illegal activity because various people interpreted leaked emails and decorations at the restaurant as symbols of abuse. That no actual victims or witnesses came forward did not deter Welch.

Welch was convinced not by evidence for a sex ring, but rather by interpretations of ordinary things to signify something sinister. Given the lack of evidence, he and others interpreted the symbols to agree with their worldview. If I think the government is nefarious, then I think NASA faked the Moon landing. If I think that my president is ruthless, then I think that lack of evidence is evidence of murder. If I am convinced that my partner is a cheater, then small problems become evidence of my prior assumptions.

That Barack Obama’s birth certificate was an issue is evidence that people already assumed he was a foreigner. Even though candidates do not normally release their birth certificates, the lack of evidence was taken as positive evidence of illegitimacy. Even the release of his birth certificate did not dissuade some critics.

This is why we must guard against the argument from ignorance. It is easy to assume the world is exactly as we think it is. But this leads us to falsehoods and conspiracies. It is harder to only accept those conclusions that we have evidence for. But this is the way that leads to truth.