What kind of argument is made when someone asserts something must be true because it hasn't been proven false?

The argument that suggests something must be true simply because it has not been proven false is known as Appeal to Ignorance. This type of reasoning relies on a lack of evidence against a proposition as a basis for accepting it as true. The flaw in this argument lies in assuming that absence of evidence against a claim is sufficient justification for its acceptance. Just because something hasn't been disproven does not necessarily mean it is true; it merely indicates a gap in evidence regarding that claim.

This argument illustrates a misunderstanding of how knowledge and truth are established. In logical discourse, evidence and reasoning should guide conclusions, rather than the mere lack of counter-evidence. Understanding this distinction is crucial in evaluating arguments critically. Other types of arguments, like Ad Hominem or False Dilemma, represent different logical fallacies and don't pertain to the reasoning of asserting a claim based solely on the absence of disproof. Victory by Definition also does not apply here, as it refers to a specific tactic of redefining terms to win a debate rather than discussing the validity of a claim based on evidence.