Appeal to Ignorance _ claiming the unknown; specifically when someone argues that a statement is true simply because it has never been proven false. (argumentum ad ignorantiam)
There is no evidence against “X”. Therefore, “X”.
There is no evidence for “X”. Therefore, “X”.
If “X” were true, then I would know that “X”.
I don’t know that “X”. Therefore, “X” is false.
The Appeal to Ignorance fallacy occurs when lack of evidence is used as evidence in an argument. If positive evidence for the conclusion is found, then we have reasons for accepting it, but a lack of evidence by itself is no evidence.