Moral dilemmas often pit narrow self-interest against the greater good. You observe a mate abusing his partner: do you have him on and possibly jeopardise the friendship or decide it's none of your business?
You're aware a colleague is behaving unprofessionally: do you alert the boss or decide it's above your pay grade? You recognise the delinquent in the CCTV footage as your neighbour's son: do you dob him in or take the path of least resistance?
No one knows for sure what became of the English aristocrat Lord Lucan, who murdered his children's nanny thinking she was his wife.
But whether he ended up at the bottom of the English Channel or in a hippie colony in Goa, his disappearance was almost certainly aided and abetted by upper-class gambling friends who put class solidarity ahead of the minor matter of a bludgeoned-to-death commoner.
Then there's the horrific example of the employees and managers at the BBC who were more concerned about the institution's reputation than whatever was going on behind the locked door of Jimmy Savile's dressing room.
The choice is between being a good mate/relative/neighbour/colleague or a good citizen.
Whichever you choose, there will be consequences: assuming they have consciences, imagine the shame, as the scale of Savile's crimes became apparent, of those who knew or suspected he was a predator all along.
Someone who did do the right thing is the woman who told authorities where her cousin, the mastermind of last November's terrorist outrage in Paris, was holed up. She's now in hiding.
And so we turn our gaze to America and, unavoidably, Donald Trump.
Last week Mitt Romney, the 2012 Republican presidential candidate, made an extraordinary intervention in the campaign. Trump, he said, is a fraud and a phoney whose brand is built on dishonesty. The core of his personal narrative and political sales pitch - that he's a money-making genius whose Midas touch will be deployed for the benefit of all - is a lie. His domestic policies would cause a recession while his foreign policies would make America and the world less safe. His most evident characteristics - "bullying, greed, showing off, misogyny, absurd third-grade theatrics" - make him unfit for the White House.
Romney's unsparing verdict was seconded by John McCain, the 2008 Republican presidential candidate and, in varying degrees by Trump's remaining rivals in the race for the Republican nomination.
And what effect has this unprecedented condemnation of a party's frontrunner had? Either absolutely none or, as Trump would have it, the opposite of what was intended since his support has, if anything, increased.
Given that it appears more likely by the day that Trump will secure the nomination what will his Republican critics do then?
You'd think it was clear-cut. If they genuinely believe Trump is unfit for high office and poses a clear and present danger to America's prosperity and security, then surely they must do everything in their power, up to and including supporting the Democratic candidate, to stop him.
Apparently not. Trump's rivals have declared they will support the nominee, whoever he is. Senior Republicans in Congress have indicated likewise. The old conservative catch-cry "my country, right or wrong" has mutated into "my party, right or wrong".
The lack of logic and principle involved is revealed in their self-justification: that it would be unthinkable to facilitate a Hillary Clinton victory. Yet Clinton is the archetypal pragmatic centrist, derided by left-wing critics for her ties to Wall St and hawkish foreign policy.
In terms of temperament and ideology, it's hard to believe a Democratic candidate could be any more palatable to the Republican establishment.
American conservatives trumpet their patriotism at every opportunity yet faced with this dilemma they intend to follow the example of English novelist E.M. Forster, who said, "If I had to choose between betraying my country and betraying my friend, I hope I should have the guts to betray my country."
What makes it even worse is that Trump is not their friend.
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