What is described as a fallacy that relies on an opponent's inability to disprove a conclusion?

The concept described is known as an appeal to ignorance, which posits that a claim is true simply because it has not been proven false, or vice versa. This fallacy exploits the lack of evidence to disprove a claim and asserts that the absence of evidence is sufficient to validate the conclusion being drawn.

For example, if one were to say that a certain health policy is effective because no studies have proven it ineffective, they are employing an appeal to ignorance. It sidesteps the need for substantiated evidence to support either side of the argument and instead relies on the opponent's inability to counter the assertion, which weakens rational debate.

Other options do not fit this description. An appeal to emotion focuses on manipulating feelings rather than logical reasoning, the straw man argument involves misrepresenting an opponent's position to make it easier to attack, and ad hominem attacks direct criticisms towards the individual instead of addressing the argument itself. Each of these fallacies distracts from the logical validity of evidence, while the appeal to ignorance specifically hinges on the absence of disproving evidence as a means to claim truth.