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  2. Necessity and sufficiency - Wikipedia

    en.wikipedia.org/wiki/Necessity_and_sufficiency

    For example, at present, "today is the Fourth of July" is a necessary and sufficient condition for "today is Independence Day in the United States". Similarly, a necessary and sufficient condition for invertibility of a matrix M is that M has a nonzero determinant. Mathematically speaking, necessity and sufficiency are dual to one another.

  3. Affirming the consequent - Wikipedia

    en.wikipedia.org/wiki/Affirming_the_consequent

    In propositional logic, affirming the consequent (also known as converse error, fallacy of the converse, or confusion of necessity and sufficiency) is a formal fallacy (or an invalid form of argument) that is committed when, in the context of an indicative conditional statement, it is stated that because the consequent is true, therefore the ...

  4. Logical consequence - Wikipedia

    en.wikipedia.org/wiki/Logical_consequence

    Logical consequence is necessary and formal, by way of examples that explain with formal proof and models of interpretation. [1] A sentence is said to be a logical consequence of a set of sentences, for a given language , if and only if , using only logic (i.e., without regard to any personal interpretations of the sentences) the sentence must ...

  5. Biological tests of necessity and sufficiency - Wikipedia

    en.wikipedia.org/wiki/Biological_tests_of...

    Biological tests of necessity and sufficiency refer to experimental methods and techniques that seek to test or provide evidence for specific kinds of causal relationships in biological systems. A necessary cause is one without which it would be impossible for an effect to occur, while a sufficient cause is one whose presence guarantees the ...

  6. Antecedent (logic) - Wikipedia

    en.wikipedia.org/wiki/Antecedent_(logic)

    Examples: If , then . This is a nonlogical formulation of a hypothetical proposition. In this case, the antecedent is P ... Necessity and sufficiency; References

  7. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...

  8. Category:Necessity and sufficiency - Wikipedia

    en.wikipedia.org/wiki/Category:Necessity_and...

    Pages in category "Necessity and sufficiency" The following 5 pages are in this category, out of 5 total. This list may not reflect recent changes. ...

  9. Logical truth - Wikipedia

    en.wikipedia.org/wiki/Logical_truth

    A statement is logically true if, and only if its opposite is logically false. The opposite statements must contradict one another. In this way all logical connectives can be expressed in terms of preserving logical truth. The logical form of a sentence is determined by its semantic or syntactic structure and by the placement of logical constants.