Albert Einstein and Niels Bohr were together at Paul Ehrenfest’s home in Leiden in December 1925. The three friends were relaxing in the drawing room after enjoying an excellent meal, which Ehrenfest, a skilled cook, had prepared himself. Bohr sipped his port, gave a great sigh of satisfaction and complemented his host on the quality of the roast lamb they had just enjoyed together.
“I must say, you are a master chef,” said Bohr to Ehrenfest. “That lamb was absolutely delicious. I don’t think I’ve ever tasted such a fine roast, and lamb is such a difficult meat to cook well. You must tell me how you managed to ensure the meat was both tender and succulent throughout the whole joint. There was not a bit of it that was dry or overdone!”
Ehrenfest shot a shrewd glance at Bohr, and said, “I think the secret is to keep the heat constant throughout the entire cooking process, which itself must proceed very slowly.”
The three men sat deep in thought for a while.
Presently, Ehrenfest rose and drained his glass. He excused himself, telling his friends that an idea had just occurred to him. He left the room in search of paper and pen.
After their host had left the drawing room, Bohr turned to Einstein, who was lighting his after-dinner pipe.
“Albert,” said Bohr, “Are you not concerned over the antics of Herr Hitler and those brown-shirted ruffians of the National Socialist German Workers’ Party? It seems to me they present a grave threat to young Weimar Republic. Herr Hitler openly disparages the very idea of democracy, and proposes a one-party state. Do you think Hitler will come to power in Germany?”
Einstein first took a few thoughtful puffs on his pipe. Then he ruffled his unruly hair, and said, “It really depends on how you look at it: Power might well come to him.”
Bohr looked somewhat exasperated. The two of them lapsed into a silence, which for a while was broken only by gentle sipping sounds as they finished their glasses of port. However, after a few minutes, Bohr pressed on, as he valued his great friend’s opinion.
“But are you not in the least concerned over the way things seem to be going?” Bohr said. ”I have read some of the nonsense that that upstart Austrian corporal is spouting about ensuring the racial purity of the German nation. You’re Jewish, Paul’s Jewish, and although I’m not German I’m half-Jewish. In what direction is Hitler’s movement going? In matters related to the Jewish Question, do you know his position?”
Einstein leaned back in his comfortable armchair, and, stretching his right hand back behind his shoulder, rubbed the nape of his neck in luxurious contemplation. Then he turned to Bohr and gave the younger man a gentle smile.
“I think it’s very difficult to give a 100-percent certain answer to either of those last two questions, and I quite definitely couldn’t answer them both at the same time,” he said.