Op (‘If something is, then it should be like that’) and, in principle,
p Op
p (‘what ought to be, is achieved’).
Note what this actually means. A statement p has a truthvalue 1 (true) or 0 (false), depending upon the state of the world. A statement Op has a ‘truthvalue’ 1 (ought) or 0 (not-ought) depending upon one’s preferences. Applying the logical calculus for the propositional operators
, ~,
, & thus is a mental exercise, where empirical and preferential statements are first given the common denominator of ‘accepting as valid’. Also, it may be that in one case both p and Op are accepted, but the rejection of