It is a commonly held opinion that John B. Watson's behaviorism was a species of philosophical materialism. Edna Heidbreder, for instance, spoke of it as "flaunting" a materialism that was "after all a very ancient philosophy" (1933, p. 138). The popular philosopher C. E. M. Joad (1948) saw it as a form of "modern materialism," modern apparently only because it occurred in the 20th century. So far as I know, this understanding has never been seriously challenged.¹