Dear Bob, The history of probability goes back much further than 1960. In fact, the roots are in Laplace's work, who in 1774 formalized the ideas of Bernoilli and Bayes. See for instance http://bayes.wustl.edu/etj/articles/stand.on.entropy.pdf and many other interesting articles on Jaynes' page.
Bert Kappen SNN University of Nijmegen tel: +31 24 3614241 fax: +31 24 3541435 URL: www.snn.kun.nl/~bert
