The next time someone lectures you about the common good, try this experiment: Ask them to name four or five circumstances in which their own political positions are at odds with the public interest and explain how they would go about subordinating them to that public interest. What you will learn in practically every case is that everyone thinks the public interest is identical to his own desires and priorities, which is why discussions along those lines have gone nowhere for the past 200 years or so in any reasonably developed society with more cultural and religious diversity than Denmark.
(Thanks, @ReaderJohn )