[Ramesh Patil <RAMESH@VAXA.ISI.EDU>: Re: Recursive Defs]Ramesh Patil <RAMESH@vaxa.isi.edu>
Date: Fri 27 Jul 90 14:41:42-PDT
From: Ramesh Patil <RAMESH@vaxa.isi.edu>
Subject: [Ramesh Patil <RAMESH@VAXA.ISI.EDU>: Re: Recursive Defs]
Posted-Date: Fri 27 Jul 90 14:35:38-PDT
Received-Date: Fri, 27 Jul 90 14:35:40 -0700
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Date: Fri 27 Jul 90 14:35:38-PDT
From: Ramesh Patil <RAMESH@VAXA.ISI.EDU>
Subject: Re: Recursive Defs
After looking at Bernhard's definition of human, I am not sure
that that example serves as a good example for testing fixed point
semantics. There are a number of problems, first our understanding of
human is a ``natural kind'' not a defined concept. Second if
every human being had two parents as defined, then we do not have
the base case for induction, we need to posit that Adam and Eve
are human and then one has a base case.
Similarly, we cannot say that offsprings of human are human. The definition
only states that offsprings of TWO humans are human. Thus the counterintutive
results derieved from least and greatest fixed point are really not
counterintutive, given the definition. It is also not surprising that
defintion of human is no different from that of dog or cat or any other animal.
TThis should be expected given the definition of human and given that there
is no special meaning attached to the names of these definitions.
I think as dave Mcallester suggests, we need to give fixed point
semantics more serious consideration.