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fallacy , contradiction and invalid argument are same or different

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Tautology: Compound preposition which is always True.

i.e P∨P~=T

Contradiction: Compound preposition which is always False.

i.e.P∧P~=F

Contingency: Compound preposition which is sometimes True and sometimes False.

i.e.

P Q P ∧ Q
T T T
T F F
F T F
F F F

Satisfiability: A Compound preposition is satisfiable if there is at least one True in its truth table.

So, Tautology is always satisfiable.

Unsatisfiability: Not even a single True result in its truth table.

FALLACIES :-A type of argument is a fallacy of propositional logic when two conditions are met: Itspropositional form is non-validating.

I hope this helps..

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A contradiction is when a proposition is always false.

A valid proposition is when it is always true ..i.e. a tautology. So, an invalid proposition can be a contingency or a contradiction.

A fallacy is when one has used at least one invalid proposition to reach the conclusion.

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hitendra singh asked Oct 22, 2018
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State T/F:1- Every satisfiable is a contingency2- Every satisfiable is a Tautology.