One of the Prefaces to the 2011 Routledge Classics edition of Karl Popper’s famous The Open Society and its Enemies bears the following footnote:
The Chancellor’s Lecture for 1995, Stout Research Centre, Victoria University of Wellington, New Zealand. Given on the occasion of the visit of Václav Havel, the former President of the Czech Republic, to the University to receive an Honorary Doctorate of Literature. 1995 was the fiftieth anniversary of the publication of The Open Society and its Enemies.
Václav Havel titled his lecture, Karl Popper’s "The Open Society and its Enemies in the contemporary global world," and in the opening paragraph we read:
He [Karl Popper] was a world traveller who followed the biggest war ever waged by humankind – the war unleashed by the tribal fury of Nazi ideology – from this country, from New Zealand. It was here that he thought about the state of the world, and it was here that he wrote his most important books. …He posed the question why is was so difficult for the idea of an open society to prevail against wave after wave of tribalism, and inquired into the spiritual background of all enemies of open society and into the patterns of their thinking, (emph. AP)
Both Karl Popper and Václav Havel were acutely aware of the “tribal fury of Nazi ideology”. So profoundly overwhelming were their experiences that neither Popper, nor Havel can be blamed for failing to notice the tribal fury of Islamic ideology making ready in the pre-dawn darkness. “Muhammad is the messenger of Allah. And those with him are ruthless against the unbelievers and merciful among themselves.” (Qur’an 48:29)