paralogism

A fallacious or illogical argument or conclusion.

In logic, fallacious argument or false reasoning; reasoning which is false in form—that is, in which the conclusion does not follow from the premises; a conclusion unwarranted by the premises.

A reasoning which is false in point of form, that is, which is contrary to logical rules or formulæ; a formal fallacy, or pseudo-syllogism, in which the conclusion does not follow from the premises.

A fallacious argument or illogical conclusion, especially one committed by mistake, or believed by the speaker to be logical.

an unintentionally invalid argument