 The approach revived ideas from <unk> and control theory that had been unpopular since the sixties . Another precursor was David <unk> , who had come to MIT in the late 70s from a successful background in theoretical <unk> to lead the group studying vision . He rejected all symbolic approaches ( both McCarthy 's logic and Minsky 's frames ) , arguing that AI needed to understand the physical machinery of vision from the bottom up before any symbolic processing took place . ( <unk> 's work would be cut short by leukemia in 1980 . ) 
