Ok, this must be a simple derivation, but it has eluded me. I'm trying to prove that the following argument is valid in first order predicate logic: 'Any creature with a kidney has a heart. Therefore, nothing with a kidney lacks a heart.'
Symbolised, it's: (Ax) (Kx > Hx) therefore ~ (Ex) (Kx & ~Hx)
Where (Ax) is a universal quantifier, (Ex) an existential quantifier, > is a material conditional.
What's the derivation!?