A person claims that their idea is best because nobody has proven it wrong. Which fallacy are they using?

The claim that an idea is the best simply because no one has proven it wrong is known as an "Appeal to Ignorance." This fallacy occurs when someone argues that a lack of evidence against a claim serves as proof of its validity. In essence, they are suggesting that because there is no opposing evidence, their position must be true.

This argument does not engage with the actual merits of the idea or provide substantive proof in favor of it; rather, it relies on the absence of disproving evidence. Hence, it circumvents the need for a rational case based on facts or logical reasoning. This approach misleads the audience by suggesting that an idea's truth is guaranteed by the failure of others to prove it false, rather than through positive evidence supporting the claim.