JMC@SAIL.STANFORD.EDU (John McCarthy) (07/17/87)
[In reply to message sent Tue 14 Jul 1987 22:58-PDT.] The distinction I had in mind between natural kind and cluster is the presumed existence of as yet unknown properties of a natural kind. When I said "doubtful cases are rare", I left myself open to misunderstanding. I meant that in case of chairs in Timothy's experience doubtful cases are rare. Therefore, for a child to presume a natural kind on hearing a word or seeing an object is advantageous, and it will also be advantageous to built AI systems with this presumption. Finally, a remark concerning the "symbol grounding" discussion. My problems with it were mainly quantitative - there was just too much to follow. I suspect that Stevan Harnad's capacity to follow very long discussions is exceptional. I would welcome a summary of the different points of view by someone who did follow it and feels himself sufficiently uncommitted to any single point of view.