'What kind of mathematics are you interested in?' Danny asked…

'I'm really interested in logic. Mathematical logic.'

He looked puzzled.

'Some people call it symbolic logic,' I said.

'I never even heard of it,' he confessed.

'It's really very new. A lot of it began with Russell and Whitehead and a book they wrote called Principia Mathematica.'

'Bertrand Russell?'

'That's right.'

'I didn't know he was a mathematician.'

'Oh, sure. He's a great mathematician. And a logician, too.'

'I'm very bad at mathematics. What's it all about? Mathematical logic, I mean.'

'Well, they try to deduce all of mathematics from simple logical principles and show that mathematics is really based on logic. It's pretty complicated stuff. But I enjoy it.'

'You have a course in that in your schoo!?'

'No. You're not the only person who reads a lot.'

For a moment he looked at me in astonishment. Then he laughed.

'I don't read seven or eight books a week, though, like you,' I said. 'Only about three or four.'

He laughed again. Then he got to his feet and stood facing me.

His eyes were bright and alive with excitement.

'I never even heard of symbolic logic,' he said. 'It sounds fascinating. And you want to be a rabbi? How do they do it? I mean, how can you deduce arithmetic from logic? I don't see -!

He stopped and looked at me. 'What's the matter?' he asked.

'There's my father,' I said, and got quickly to my feet.

While mathematics is not the central topic of the book, it plays an important role. There is also a movie (with Rod Steiger) based on the novel, and a theatric piece that is still staged around the US. The main core of the book is about religion and friendship.