Which logical fallacy is highlighted when an argument is made based solely on the fact that the other side has not proven their case?

The highlighted logical fallacy is the Appeal to Ignorance. This fallacy occurs when one argues that a proposition is true simply because it has not been proven false, or conversely, that it is false because it has not been proven true. In this context, if one side asserts that their argument holds weight solely because the opposing side has not provided sufficient evidence, they are leveraging the absence of evidence as the basis for their conclusion.

This fallacy shifts the burden of proof away from the person making the claim, improperly asserting that a lack of proof by the other party inherently validates their own position. It's important to recognize that claims should be supported with their own evidence rather than relying on the shortcomings of the opposition's case.

The other options represent different logical fallacies and do not specifically address the scenario where the argument rests solely on the failure to prove a case, which reinforces why Appeal to Ignorance fits this description best.