"You cant prove Santa doesnt exist, therefore Santa does exist", is a common logical fallacy.
A valid syllogism contains three terms; with four it commits the logical fallacy known as quaternio terminorum.
Wikipedia foundation.
logical fallacy — noun a fallacy in logical argumentation • Hypernyms: ↑fallacy, ↑false belief • Hyponyms: ↑hysteron proteron, ↑ignoratio elenchi, ↑petitio principii, ↑petitio, ↑post hoc, ↑ … Useful english dictionary
logical fallacy — error that is based on logic … English contemporary dictionary
Burden of proof (logical fallacy) — In philosophy, the term burden of proof refers to the extent to which, or the level of rigour with which, it is necessary to establish, demonstrate or prove something for it to be accepted as true or reasonable to believe.All logical arguments… … Wikipedia
Fallacy — In logic and rhetoric, a fallacy is usually incorrect argumentation in reasoning resulting in a misconception or presumption. By accident or design, fallacies may exploit emotional triggers in the listener or interlocutor (appeal to emotion), or… … Wikipedia
Fallacy of quoting out of context — The practice of quoting out of context, sometimes referred to as contextomy or quote mining , is a logical fallacy and a type of false attribution in which a passage is removed from its surrounding matter in such a way as to distort its intended… … Wikipedia
Logical form — The form or logical form of an argument is the representation of its sentences using the formal grammar and symbolism of a logical system to display its similarity with all other arguments of the same type.It consists of stripping out all… … Wikipedia
Fallacy of division — A fallacy of division occurs when one reasons logically that something true of a thing must also be true of all or some of its parts. An example: A Boeing 747 can fly unaided across the ocean. A Boeing 747 has jet engines. Therefore, one of its… … Wikipedia
Fallacy of four terms — The fallacy of four terms (Latin: quaternio terminorum ) is the logical fallacy that occurs when a categorical syllogism has four terms.Valid categorical syllogisms always have three terms::Major premise: All fish have fins.:Minor premise: All… … Wikipedia
Fallacy of distribution — A fallacy of distribution is a logical fallacy occurring when an argument assumes there is no difference between a term in the distributive (referring to every member of a class) and collective (referring to the class itself as a whole)… … Wikipedia
Fallacy of the undistributed middle — The fallacy of the undistributed middle is a logical fallacy that is committed when the middle term in a categorical syllogism isn t distributed. It is thus a syllogistic fallacy. Pattern The fallacy of the undistributed middle takes the… … Wikipedia
