  Descartes's emphasis on decompositional analysis was not  without precedents, however. Not only was it already involved in  ancient Greek geometry, but it was also implicit in Plato's  method of collection and division. We might explain the shift from  regressive to decompositional (conceptual) analysis, as well as the  connection between the two, in the following way. Consider a simple  example, as represented in the diagram below,  ‘collecting’ all animals and ‘dividing’ them  into rational and non-rational, in order to define  human beings as rational animals.