Montag is sitting with men who used to be professors, doctors, reverends, etc. The point is they are all very intelligent, and have been banned by the society. They cannot physically carry books with them though, it would be too obvious. These men have read the books, then they learned how to memorize them, and the certain important phrases. So they can tell people what is in the books and such because they have taught themselves how to remember anything that they have read once.