**counterexamples** — n. example that refutes a theory or claim; example used to prove that a statement is false … English contemporary dictionary

**Counterexamples in Topology** — Author(s) Lynn Arthur Steen J. Ar … Wikipedia

**Frankfurt counterexamples** — (also known as Frankfurt cases or Frankfurt style cases) were presented by philosopher Harry Frankfurt in 1969 as counterexamples to the principle of alternative possibilities or PAP, which holds that an agent is morally responsible for an action … Wikipedia

**Counterexample** — In logic, and especially in its applications to mathematics and philosophy, a counterexample is an exception to a proposed general rule. For example, consider the proposition all students are lazy . Because this statement makes the claim that a… … Wikipedia

**Gettier problem** — A Gettier problem is a problem in modern epistemology issuing from counter examples to the definition of knowledge as justified true belief (JTB). The problem owes its name to a three page paper published in 1963, by Edmund Gettier, called Is… … Wikipedia

**Four color theorem** — Example of a four colored map A four colori … Wikipedia

**Constructive proof** — In mathematics, a constructive proof is a method of proof that demonstrates the existence of a mathematical object with certain properties by creating or providing a method for creating such an object. This is in contrast to a nonconstructive… … Wikipedia

**Seifert conjecture** — In mathematics, the Seifert conjecture states that every nonsingular, continuous vector field on the 3 sphere has a closed orbit. It is named after Herbert Seifert. In a 1950 paper, Seifert asked if such a vector field exists, but did not phrase… … Wikipedia

**Tychonoff space** — Separation Axioms in Topological Spaces Kolmogorov (T0) version T0 | T1 | T2 | T2½ | completely T2 T3 | T3½ | T4 | T5 | T6 In topology and related branches of mathematic … Wikipedia

**Raven paradox** — The Raven paradox, also known as Hempel s paradox or Hempel s ravens is a paradox proposed by the German logician Carl Gustav Hempel in the 1940s to illustrate a problem where inductive logic violates intuition. It reveals the problem of… … Wikipedia