Unformatted text preview: * All humans are mortal. *Socrates is human. * Socrates is mortal. ∴ We agreed on the symbolization of this argument in our definition-style demonstration of its validity, so we can begin our first predicate derivation: It is pretty obvious here that there is not much we could do at this point with the second premise, so we use ∀ E right away. The only choice we need to make in applying this rule is what term we wish to use for the substitution instance, that is, the constant or variable we want to be our instantiating term. Seeing as anything other than s won't be of much help, s it will be: Not so difficult, is it? We are actually only one step away from completing the derivation—all we need to do is apply →E, and we are done:...
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- Winter '09
- Logic, φ, substitution instance, original predicate argument, universal elimination