Some evidence concerning the genesis of Shannon’s information theory

A typescript by Claude Shannon, ‘Theorems on statistical sequences’, (donated to the Library of Congress in 2001 and apparently unscrutinized by historians to date) is examined to shed light on the development of information theory. In particular, it appears that Shannon was still working out the mathematical details of his theory in the spring of 1948, just before he published ‘A mathematical theory of communication’. This is contrasted with evidence from a declassified cryptography report that Shannon’s theory was intuitively worked out in its essentials by the time he filed the report in 1945. Previous interviews with Shannon, and a recent interview with a colleague of his, Brockway McMillan, confirm this picture.