What's behind the recent eruptions of anti-Semitism?
Sean Spicer's Hitler remark may have been just ignorant, but there are others
All Western governments oppose anti-Semitism.
Yet the old hatred continues.
How toxic is it? And are recent eruptions of anti-Semitism expressions momentary irritations, misunderstandings or plain ignorance?
White House press secretary Sean Spicer could, on a kindly view, fall into the last of these categories.
His remark that Adolf Hitler used no chemical weapons, made at his press conference last week, was followed by outrage and instant contrition.
Mr Spicer meant that Hitler did not drop chemical bombs from airplanes - an accurate observation, and one made later in the day by Defence Secretary James Mattis.
The Nazis used Zyklon B in their death camps, and Hitler may have refrained from using chemical weapons in the battlefield for tactical reasons.
If Mr Spicer had a wider frame of reference, he might have either refrained from the comparison or been explicit about where Nazis used chemical weapons and on whom.
But his comment was not necessarily a sign of racism.
Even so, Mr Spicer serves an administration that, in a statement commemorating International Holocaust Remembrance Day in January, did not mention Jews.
Meanwhile, US President Donald Trump's senior adviser Steve Bannon, through his embrace of the "alt right", has been dogged by claims of anti-Semitism.
The President's son-in-law Jared Kushner and daughter Ivanka are Jewish, and the couple is seen as a moderating presence in the White House.
A recent eruption in the United Kingdom does not give much more clarity on the state of anti-Semitism.
Mr Ken Livingstone, a prominent member of the Labour Party and a former mayor of London, repeatedly argued that Hitler was a Zionist - that is, he believed in the establishment of the state of Israel.
The claim was quite thoroughly discredited, and many saw it as anti-Semitic.
Yet, could it have been a simple mistake? Mr Livingstone denied any trace of anti-Semitism.
He was banned from holding office in the Labour Party for a year - a sanction many Labour Party MPs and members found too soft, and against which deputy leader Tom Watson strongly protested, calling for his expulsion.
The conflict illuminates a split on the left everywhere in the West.
On one side are those who see Israel as the largest problem in the Middle East and who, to some degree, agree with organisations such as Hezbollah and Hamas - both dedicated to destroying Israel.
On the other side are those who, even while condemning the current Israeli government for its settlement and other policies, support the continued existence of the Jewish state.
Current Labour Party leader Jeremy Corbyn originally belonged to the first group, and he called both Hezbollah and Hamas "friends" - a characterisation he later said he regretted.
In France, the Western country most plagued by terrorism and attacks on Jews, the good news seems to be that the National Front, which under previous leader Jean-Marie Le Pen was fiercely anti-Semitic, has under his daughter Marine cleansed itself of the virus. Or has it?
Recent reporting points to Mr Frederic Chatillon, a close adviser to the younger Le Pen, as being an active anti-Semite - a sign to some that the National Front has not fundamentally changed, and cannot do so, while many of its rank and file still revere the older Le Pen for speaking the truth.
A Le Pen presidency would increase the fear in which many French Jews live and drive more to emigrate to Israel.
In a revealing piece in Vanity Fair, a retired police commissioner named Sammy Ghozlan - the most active campaigner against anti-Semitic incidents and attacks - moved to Israel.
The old lie is still active in central Europe - in Hungary, where the far right Jobbik Party won some 20 per cent of the vote and one-third of the population expressed themselves as anti-Semitic; and in Poland, where a recent survey showed that more than half would not accept a Jew as a family member and almost a third would not wish to have Jews as neighbours.
What Jews know, even those in the generations born since the Holocaust, is that times when nationalism, insecurity and populist politics are on the rise never bring them good.
They depend on liberal politics surviving and remaining strong: another good reason why it should.
John Lloyd co-founded the Reuters Institute for the Study of Journalism at the University of Oxford, where he is senior research fellow.