 For his more empirically-minded students, Anderson’s logic seemed to rely upon an unwelcome element of a priorism. Any weakening of our confidence in Anderson’s identification of logic and ontology, for example, would critically undermine significant components of the position. First, it would no longer be clear that things spoken of together must exist in the same way – the notion of a single level of being would become a matter for investigation (what kinds of differences exist) rather than determined by general principle (Mackie 1985). Regarding his social thought, the importance of individuals’ behaviour in explaining the nature and operation of social movements and institutions would require investigation, rather than a pronouncement based purely on general grounds. Again, Anderson’s rejection of the rationalist view that there must be simple or ultimate units upon which complex things can be built would not lead without further argument to the view that there cannot be such simple parts or totalities (Mackie 1985).