Logic puzzle Logic puzzle A logic puzzle is a puzzle deriving from the mathematics field of deduction. The logic puzzle was first produced by Charles Lutwidge Dodgson, who is better known under his pen name Lewis Carroll, the author of "Alice's Adventures in Wonderland". In his book "The Game of Logic" he introduced a game to solve problems such as confirming the conclusion "Some greyhounds are not fat" from the statements "No fat creatures run well" and "Some greyhounds run well". Puzzles like this, where we are given a list of premises and asked what can be deduced from them, are known
Logical equivalence if and only if formula_2'". In particular, the truth value of formula_7 can change from one model to another. The claim that two formulas are logically equivalent is a statement in the metalanguage, expressing a relationship between two statements formula_1 and formula_2. The statements are logically equivalent if, in every model, they have the same truth value. Logical equivalence In logic, statements formula_1 and formula_2 are logically equivalent if they have the same logical content. That is, if they have the same truth value in every model (Mendelson 1979:56). The logical equivalence of formula_1 and formula_2 is sometimes expressed as