Given this definition:
A deduction is valid if and only if its conclusion is true whenever all of its hypotheses are true.
Can an argument be valid if it has a tautology as a conclusion?
An example I can think of is:
- A proposition is either a tautology or not a tautology
- (1) is a proposition
- (1) is either a tautology or not a tautology
That seems strange/wrong to me, even though it appears to meet the definition. Are there other conditions for an argument to be valid?