Sentence:  Accordingly , it is the aim of this essay to advance a new theory of imitation ( which I shall call mimesis in order to distinguish it from earlier theories of imitation ) and a new theory of invention ( which I shall call symbol for reasons to be stated <WSD>hereafter</WSD> ) . 
Meaning of the word marked with <WSD> tags:  in a subsequent part of this document or statement or matter etc.