Ad ignorantium

The fallacy is committed when one asserts that a proposition is true because it has not yet been proven false or a proposition is false because it has not yet been proven true. If a proposition has not yet been proven true, one is not entitled to conclude, solely on that basis, that it is false, and if a proposition has not yet been proven false, one is not entitled to conclude, solely on that basis, that it is true.

Nothing is known about A. Yet a conclusion is drawn about A.

Facts may be given all around a particular subject, yet nothing specific is said about the subject. Based on this circumstantial evidence, it is assumed that something may be known about A.

A variant occurs where a lack of evidence is assumed to be proof, for example when a murder suspect does not have an alibi.

Circumstantial evidence is well known in the courtroom as being very weak evidence, if evidence at all. Yet in daily life it is used with impunity. Yet the notion of a person being innocent until proven guilty also makes conclusions without proof. Similarly, scientists largely assume something does not exist until it is proven.

A significant question with this is where the burden of proof lies. Is it with the prosecutor or the defendant? Usually it is with the person making a claim that something exists or has happened.