3 ms·

“Ducks are mammals” contradicts “mammals have mammary glands”. When this type of contradiction happens, we call the logical system inconsistent.

• aidenn0 4y ago
  It's still logically consistent if I claim that ducks have mammary glands, and any duck to the contrary has had them surgically removed by the government. You hand me an egg to put in my own incubator and raise myself? Well someone swapped the duck while I wasn't looking before the mammary glands developed.
• SAI_Peregrinus 4y ago
  "mammals have mammary glands" was not a listed axiom. There are two axioms, of the forms: "all X perform action Y", and "All D are members of X". There conclusion of the form "All D perform action Y" is sound. The second axiom contradicts observation, but axioms don't have to correspond to reality for the logic to be sound.
  • dragonwriter 4y ago
    > "mammals have mammary glands" was not a listed axiom. There are two axioms, of the forms: "all X perform action Y", and "All D are members of X". There conclusion of the form "All D perform action Y" is sound. No,valid, not sound. Soundness is validity plus true premises, and any sound conclusion is true of logical necessity. A valid conclusion is true contingent on the truth of the supporting premises. > but axioms don't have to correspond to reality for the logic to be sound. False, premises being true is part of the definition of soundness.