To keep up with debates at the talmudic academy in ancient days, you had to have a pretty good memory. Since manuscripts were scarce, whatever information you wanted to support your argument needed to be stored inside your head.
Fast forward 2,000 years and the modern yeshivah student has no need to keep a library in his brain. On his laptop he can surf not only classic sources like the Talmud but a vast amount of subsequent halachic literature.
The digitalisation of Jewish knowledge we now take for granted is thanks to men like Professor Aviezri Fraenkel of Israel's Weizmann Institute, the founder of one of the best-known databases, the Global Jewish Responsa Project. Apart from primary sources like the Code of Jewish Law, it enables users to search more than 110,000 responsa - instances of rabbinic case law - down the ages, plus another 14,000 articles.
"In Hebrew, there is an expression 'the sea of the Talmud', it is so huge," he said. "If the Talmud is a sea, I'd call the responsa an ocean because it is much bigger."
But like many pioneers, he had to struggle against a good deal of scepticism when he first dreamed of putting the rabbis on computer more than 50 years ago.
Einstein wondered 'what such a small country would do with such a big computer'
At 86, he still has an office at the Weizmann and made a lecture tour of the United States last year. Born in Munich, he grew up in Switzerland after the Nazis came to power; his family emigrated to Palestine the year before the outbreak of war. A religious man, he has spent most of his career at the Weizmann, the institution which embodied the aspirations of Israel's first president to be at the forefront of scientific endeavour.
Starting out as an engineer, he helped to construct Israel's first computer, the Weizac in the mid-50s. "The computer occupied a huge hall and adjacent to it was a building for air-conditioning it - it contained 2,300 radio tubes," he recalled. "Each tube was heated and if you didn't cool it, the whole thing would melt down."
But even Einstein, he said, questioned the rationale and wondered "what such a small country would do with such a big computer".
By the time he completed his doctorate in the United States, he had switched to maths and eventually became head of maths at Bar-Ilan University. His speciality is combinatorial game theory.
When Weizmann was building a new computer Golem to replace Weizac, he was asked to go back to the States to Minneapolis to look at an interim computer. "I was staying in a hotel but on Shabbat I was hosted by a family called Kutoff," he said. "One day Mr Kutoff asked me what could a computer do for Judaica. And this question of his triggered the dream of making the responsa available to everybody."
Whereas medieval commentators had cross-referenced the Talmud, there was nothing comparable for the responsa literature. "The responsa literature was like a sealed book," he said. "Nobody knew exactly what was in or wasn't in it."
But when he mentioned the idea of having a database on which you could carry out a search on the whole text, "there was very strong opposition... You have to imagine the atmosphere in 1963. It was 35 years before Google."
He remembers one of Israel's leading mathematicians dismissing the concept of full-text search as utopian. In the meantime, a team at the Hebrew University was trying to compile a manual index of the responsa.
The difficulty with responsa is that it is not just enough to catalogue a title. A single work could contain multiple topics and sub-topics - and a theoretical question might actually conceal something of practical relevance. A medieval rabbi's discussion of a hypothetical issue about sacrifices, for example, might make a legal point that will be applicable to kosher meat.
Undeterred, Professor Fraenkel did not give up - although the manual index team eventually did, some years later.
The responsa project, which he directed from 1963 to 1974, moved with him to Bar Ilan. In the early days, if you wanted to put a question to a computer, you had to go through the laborious process of translating the query into computer language, punched on to cards fed to the machine, and then wait patiently for the answer.
When computers started being designed that could recognise letters, naturally it was the Roman alphabet that was used first. One day Professor Fraenkel was having lunch with the visiting American inventor Jacob Rabinow. "I asked him, can you make a machine that can read Hebrew. He said no problem. He took one of our books to show to his engineers and after a very long time, he cabled me and said we can do it - the first machine will cost you $200,000, but the second machine we can do for $100,000. I cabled him back: please send the second machine but don't expect immediate payment."
As technology advanced, so did the project. The CD version was launched in 1990 and the project was awarded the Israel Prize in 2007.
And now when you want to use the database, you can simply acccess 450 million words of Jewish texts on a flash drive.