2 It may not be true! x In the words of Asa Mahan: "The original proposition is called the exposita; when converted, it is denominated the converse. 2 P and , 2 c , In general, the truth of S says nothing about the truth of its converse,[1][3] unless the antecedent P and the consequent Q are logically equivalent. In mathematics, the converse of a theorem of the form P → Q will be Q → P. The converse may or may not be true, and even if true, the proof may be difficult. {\displaystyle R} T ⊆ "[8] For E propositions, both subject and predicate are distributed, while for I propositions, neither is. 2 As an example, for the A proposition "All cats are mammals", the converse "All mammals are cats" is obviously false. , , or "Bpq" (in Bocheński notation). Then the converse of S is the statement Q implies P (Q → P). is also called the transpose. ← In practice, when determining the converse of a mathematical theorem, aspects of the antecedent may be taken as establishing context. {\displaystyle a^{2}+b^{2}=c^{2}} In natural language, this could be rendered "not Q without P". {\displaystyle P} ", "The Four Vertex Theorem and its Converse", https://en.wikipedia.org/w/index.php?title=Converse_(logic)&oldid=978919586, Articles with unsourced statements from March 2020, Creative Commons Attribution-ShareAlike License, This page was last edited on 17 September 2020, at 18:33. [5], The converse of the implication P → Q may be written Q → P, For example, consider the true statement "If I am a human, then I am mortal." 2 b , but may also be notated a For the implication P → Q, the converse is Q → P. For the categorical proposition All S are P, the converse is All P are S. Either way, the truth of the converse is generally independent from that of the original statement. R For A propositions, the subject is distributed while the predicate is not, and so the inference from an A statement to its converse is not valid. a {\displaystyle P\leftarrow Q} Inference from a statement to its converse per accidens is generally valid. Logicians define conversion per accidens to be the process of producing this weaker statement. ( is a right angle. It is switching the hypothesis and conclusion of a conditional statement. c c b [9] It is therefore clear that the categorical converse is closely related to the implicational converse, and that S and P cannot be swapped in All S are P. William Thomas Parry and Edward A. Hacker (1991), "The Definitive Glossary of Higher Mathematical Jargon — Converse", "What Are the Converse, Contrapositive, and Inverse? Conversion is valid when, and only when, nothing is asserted in the converse which is not affirmed or implied in the exposita. b In logic and mathematics, the converse of a categorical or implicational statement is the result of reversing its two constituent statements. {\displaystyle \forall x.S(x)\to P(x)} {\displaystyle R^{T}=\{(b,a):(a,b)\in R\}} Thus, the statement "If I am a triangle, then I am a three-sided polygon" is logically equivalent to "If I am a three-sided polygon, then I am a triangle", because the definition of "triangle" is "three-sided polygon". = The converse, which also appears in Euclid's Elements (Book I, Proposition 48), can be stated as: Given a triangle with sides of length Example: "if you are a dog then you bark". {\displaystyle a^{2}+b^{2}=c^{2}} See also. b For example, the Four-vertex theorem was proved in 1912, but its converse was proved only in 1997.[4]. {\displaystyle R\subseteq A\times B,} For example, the converse of "If it is raining then the grass is wet" is "If the grass is wet then it is raining." However, if the statement S and its converse are equivalent (i.e., P is true if and only if Q is also true), then affirming the consequent will be valid. ∈ ⊂ P {\displaystyle c} , if the angle opposite the side of length This is equivalent to saying that the converse of a definition is true. In first-order predicate calculus, All S are P can be represented as , In traditional logic, the process of going from "All S are P" to its converse "All P are S" is called conversion. Converse Of Alternate Interior Angles Theorem, Converse Of Basic Proportionality Theorem, Consecutive Interior Angles Converse Theorem. Switching the hypothesis and conclusion of a conditional statement. x ( then the converse relation . However, as with syllogisms, this switch from the universal to the particular causes problems with empty categories: "All unicorns are mammals" is often taken as true, while the converse per accidens "Some mammals are unicorns" is clearly false. , and For the implication P → Q, the converse is Q → P. For the categorical proposition All S are P, the converse is All P are S. Either way, the truth of the converse is generally independent from that of the original statement.[1][2]. ) Converse implication is logically equivalent to the disjunction of The validity of simple conversion only for E and I propositions can be expressed by the restriction that "No term must be distributed in the converse which is not distributed in the convertend. {\displaystyle c} In its simple form, conversion is valid only for E and I propositions:[7]. Q R × + {\displaystyle a} The converse of that statement is "If I am mortal, then I am a human," which is not necessarily true. {\displaystyle \neg Q}. In logic and mathematics, the converse of a categorical or implicational statement is the result of reversing its two constituent statements. However, the weaker statement "Some mammals are cats" is true. A conditional statement ("if ... then ...") made by swapping the "if" and "then" parts of another statement. A Q is a binary relation with {\displaystyle c} For example, the Pythagorean theorem can be stated as: Given a triangle with sides of length Consider the statement, If it is raining, then the grass is wet. c Q Let S be a statement of the form P implies Q (P → Q). {\displaystyle P\subset Q} A truth table makes it clear that S and the converse of S are not logically equivalent, unless both terms imply each other: Going from a statement to its converse is the fallacy of affirming the consequent. ) R a : R The converse is "if you bark then you are a dog". [citation needed]. . On the other hand, the converse of a statement with mutually inclusive terms remains true, given the truth of the original proposition. It is switching the hypothesis and conclusion of a conditional statement. {\displaystyle c} { S , In Mathematical Geometry, a Converse is defined as the inverse of a conditional statement. ( ) is a right angle, then {\displaystyle b} a ) P If {\displaystyle a} x Converse. ∀ = } ( In Mathematical Geometry, a Converse is defined as the inverse of a conditional statement. , then the angle opposite the side of length b B P . c b a That is, the converse of "Given P, if Q then R" will be "Given P, if R then Q". {\displaystyle b} + 2 ¬ → Also find the definition and meaning for various math words from this math dictionary. Note: As in the example, a proposition may be true but have a false converse. "[6], The "exposita" is more usually called the "convertend." a c , and , if = The converse of the statement is, If the grass is wet, then it is raining.

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