The plausible idea was that intelligence predicted the sequence of future sensations from the past sequence of sensations. Another justification for writing this up many years after I discussed it in lectures is that almost all machine learning research does not undertake to infer structures in the world and not just classify the data.
Most people think it is impossible starting from scratch.
Donald Michie said he though a good cryptographer could do it. Maybe it would take a team of cryptographers with a war to win. Many people solve it. There are html , dvi , postscript , and pdf versions of this note. The number of hits on this page since 1998 August 3.