# Pseudomathematics

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Pseudomathematics is a form of mathematics-like activity that does not work within the framework, definitions, rules, or rigor of formal mathematical models. While any given pseudomathematical approach may work within some of these boundaries, for instance, by accepting or invoking most known mathematical definitions that apply, pseudomathematics inevitably disregards or explicitly discards a well-established or proven mechanism, falling back upon any number of demonstrably non-mathematical principles.

## An illustrative contrived example

Consider the following flawed attempt at a theorem:

Theorem: All positive odd numbers are prime.
Proof: By mathematical induction.
Let $P = \{n \mid n \mbox{ is prime}\}.$
Let n = 1. Then nP.
Since n + 1 ∈ P and (n + 1) + 1 ∈ P, and skipping those divisible by 2, all numbers are prime (except those that are divisible by 2), due to induction.
Q.E.D.

While the above "proof" suffers from many flaws (such as the flawed invocation of mathematical induction and that there is no agreement that 1 is a prime), all that is required to topple it is to show a counterexample, such as the positive integer 33. This number is not prime, and if it is shown by way of arriving at a contradiction that numbers evenly divisible by any number (other than 1 or themselves) are not prime (by definition) and this thus contradicts the definition of primes, the counterargument might make an appeal such as "then the definition of primes is flawed since the above proof shows that numbers such as 33 (which is not divisible by 2) are prime."

In mathematics, a statement presenting itself as a mathematical truth is provably incorrect (that is, not a mathematical truth statement) if even one counterexample showing it to be false can be found. Indeed, a statement cannot rightly be called a "theorem" if a counterexample disproving it exists. While it is possible to call something a conjecture until a full formal evidence is given, until and unless that evidence is provided, it does not become a theorem. Conjectures, too, may be shown to be false if a counterexample exists.

An appeal that a mathematical definition is in itself wrong (i.e., that primes were somehow poorly defined in the first place) is an appeal to an argument that attacks a well-established and well-understood definition: Primes are prime by definition, and such classes of numbers may or may not have properties that make them interesting. Pseudomathematics, however, sometimes appeals to change definitions to suit its claims. At this point, pseudomathematical arguments exit the world of mathematics altogether, and even the appearance of following long-established mathematical models falls apart.

Any statement purporting to be a theorem must hold within the framework of the pre-existing definitions about which it purports to assert a truth. While new definitions may be introduced into a framework to substantiate a theorem, these new definitions must themselves hold within the framework addressed, without introducing any contradiction within that framework. Asserting that 33 is somehow prime because a flawed proof arrives at this eventuality, and then asserting that the definition of primes itself is flawed is pseudomathematical reasoning.

## Some taxonomy of pseudomathematics

The following categories are rough characterisations of some particularly common pseudomathematical activities:

1. Attempting to solve classical problems in terms that have been proven mathematically impossible;
2. Misapprehending standard mathematical methods, and insisting that use or knowledge of higher mathematics is somehow cheating or misleading.

### Attempts on classic unsolvable problems

Investigations in the first category are doomed to failure. At the very least a solution would indicate a contradiction within mathematics itself, a radical difficulty which would invalidate everyone's efforts to prove anything as trite.

Examples of impossible problems include the following constructions in Euclidean geometry using only compass and straightedge:

For more than 2,000 years many people have tried and failed to find such constructions; the reasons were discovered in the 19th century, when it was proved that they are all impossible.

## Practitioners

Pseudomathematics has equivalents in other scientific fields, such as physics. Examples include efforts to invent perpetual motion devices, efforts to disprove Einstein using Newtonian mechanics, and many other feats that are currently accepted as impossible. French psychoanalyst Jacques Lacan, and Bulgarian-French philosopher Julia Kristeva have been accused of misusing mathematics in their work; see Fashionable Nonsense (1998) by Alan Sokal and Jean Bricmont.[1]

Excessive pursuit of pseudomathematics can result in the practitioner being labelled a crank. The topic of mathematical "crankiness" has been extensively studied by Indiana mathematician Underwood Dudley, who has written several popular works about mathematical cranks and their ideas.

Not all mathematical research undertaken by amateur mathematicians is pseudomathematics. Many amateur mathematicians have produced genuinely solid new mathematical results. Indeed, there is no distinction between an amateur mathematically correct result and a professional mathematically correct result: results are either correct or incorrect, and pseudomathematical results, by relying on non-mathematical principles, are not about professionalism but about incorrectness arrived at by improper methodology.