It may be a silly doubt but I am really confused about valid and invalid terms.
From whatever I read, I concluded that:
Validity and invalidity apply only to arguments, not to propositional statements. For a (simple)statement either it can be true or false. For arguments- It is valid if all the premises are true, then the conclusion must be true. Invalid when it is possible that all the premises are true and the conclusion is false.
For a propositional formula (compound propositions) - a tautology, contingency, contradiction, satisfiable, unsatisfiable, valid terms make sense.
Now my confusion is:
- Can we use the $Invalid$ term with a compound proposition (propositional formula)? If yes, Then what is the condition for its invalidity?