Sentence:  Every attempt to derive <WSD>oughtness</WSD> from rightness must, as we have shown, either end in an illogical system or destroy the possibility of a separate science of Ethics at all. 
Meaning of the word marked with <WSD> tags:  In ethics, the quality which makes an action dutiful or morally obligatory.<ref>"Oxford English Dictionary", 3rd ed. (2004)</ref>