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Single Idea 8082

[filed under theme 5. Theory of Logic / B. Logical Consequence / 7. Strict Implication ]

Full Idea

Implication involves some form of link or causality between the antecedent and the consequent of an if-then; normally it says that the conclusion is a consequence of the premise (where conditionals are just defined by 'true' and 'false').

Gist of Idea

Where a conditional is purely formal, an implication implies a link between premise and conclusion

Source

Keith Devlin (Goodbye Descartes [1997], Ch. 2)

Book Ref

Devlin,Keith: 'Goodbye Descartes: the end of logic' [Wiley 1997], p.48


A Reaction

This distinction is a key one when discussing 'If-then' sentences. Some are merely formal conditionals, but others make real claims about where you can get to from where you are.


The 5 ideas with the same theme [it can never be that P is true and Q is false]:

Lewis's 'strict implication' preserved Russell's confusion of 'if...then' with implication [Quine on Russell/Whitehead]
Russell's implication means that random sentences imply one another [Lewis,CI on Russell/Whitehead]
Where a conditional is purely formal, an implication implies a link between premise and conclusion [Devlin]
Strict implication says false propositions imply everything, and everything implies true propositions [Mautner]
Necessary implication is called 'strict implication'; if successful, it is called 'entailment' [Girle]