ABSTRACT
(R) ‘All ravens are black’ is logically equivalent to (R–) ‘Nothing which is not black is a raven’. A white pen confirms (R–), but surely it does not confirm (R), although (R) says the same as (R–).
(R) ‘All ravens are black’ is logically equivalent to (R–) ‘Nothing which is not black is a raven’. A white pen confirms (R–), but surely it does not confirm (R), although (R) says the same as (R–).