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  2. Constructive proof - Wikipedia

    en.wikipedia.org/wiki/Constructive_proof

    Constructive proof. In mathematics, a constructive proof is a method of proof that demonstrates the existence of a mathematical object by creating or providing a method for creating the object. This is in contrast to a non-constructive proof (also known as an existence proof or pure existence theorem), which proves the existence of a particular ...

  3. Law of excluded middle - Wikipedia

    en.wikipedia.org/wiki/Law_of_excluded_middle

    Brouwer reduced the debate to the use of proofs designed from "negative" or "non-existence" versus "constructive" proof: According to Brouwer, a statement that an object exists having a given property means that, and is only proved, when a method is known which in principle at least will enable such an object to be found or constructed …

  4. Intuitionistic logic - Wikipedia

    en.wikipedia.org/wiki/Intuitionistic_logic

    Intuitionistic logic, sometimes more generally called constructive logic, refers to systems of symbolic logic that differ from the systems used for classical logic by more closely mirroring the notion of constructive proof. In particular, systems of intuitionistic logic do not assume the law of the excluded middle and double negation ...

  5. Minimal logic - Wikipedia

    en.wikipedia.org/wiki/Minimal_logic

    Minimal logic, or minimal calculus, is a symbolic logic system originally developed by Ingebrigt Johansson. [1] It is an intuitionistic and paraconsistent logic, that rejects both the law of the excluded middle as well as the principle of explosion (ex falso quodlibet), and therefore holding neither of the following two derivations as valid:

  6. Proof of impossibility - Wikipedia

    en.wikipedia.org/wiki/Proof_of_impossibility

    e. In mathematics, an impossibility theorem is a theorem that demonstrates a problem or general set of problems cannot be solved. These are also known as proofs of impossibility, negative proofs, or negative results. Impossibility theorems often resolve decades or centuries of work spent looking for a solution by proving there is no solution.

  7. Law of noncontradiction - Wikipedia

    en.wikipedia.org/wiki/Law_of_noncontradiction

    In logic, the law of non-contradiction (LNC) (also known as the law of contradiction, principle of non-contradiction (PNC), or the principle of contradiction) states that contradictory propositions cannot both be true in the same sense at the same time, e. g. the two propositions " p is the case " and " p is not the case " are mutually exclusive.

  8. Constructive analysis - Wikipedia

    en.wikipedia.org/wiki/Constructive_analysis

    The base logic of constructive analysis is intuitionistic logic, which means that the principle of excluded middle is not automatically assumed for every proposition.If a proposition . is provable, this exactly means that the non-existence claim . being provable would be absurd, and so the latter cannot also be provable in a consistent theory.

  9. Informal logic - Wikipedia

    en.wikipedia.org/wiki/Informal_logic

    Informal logic encompasses the principles of logic and logical thought outside of a formal setting (characterized by the usage of particular statements). However, the precise definition of "informal logic" is a matter of some dispute. [1] Ralph H. Johnson and J. Anthony Blair define informal logic as "a branch of logic whose task is to develop ...