Re: Vanishing Intersections

From: O'Dell, Samantha (
Date: Sun May 26 1996 - 17:46:16 BST

What is the problem of 'Vanishing Intersections'?

The classical view of categorisation is that category membership is
based on invariant features that we detect in different kinds of
stimuli. The idea of vanishing intersections is what the main objection
to this classical view is based on. It is argued that people cannot say
which features they use to define each category. Any attempt to define
the features can be rejected because there are examples of the category
that exist that do not have that feature.

The issue of vanishing intersections also arises when discussing the
poverty of the stimulus. Chomsky argues that a child cannot learn the
rules of Universal Grammar by trial and error with feedback because the
stimulus is too impoverished. Fodor and others have generalised the
problem of poverty of the stimulus from children's early grammar
learning to concepts in general, and part of this generalisation was
based on the vanishing intersections argument.
This states that it cannot be true that you learn a concept by trial
and error and feedback because the examples don't have anything in
common. For example, with concepts such as 'sensory quality' (which
includes smell, colour, sound, shapes), where all the examples of them
have nothing in common, it means the intersection vanishes. If this
occurs then how are we to know what they mean at all? It is not
possible that we learned it from sensory examples by trial and error
and feedback. Wittgenstein made a similar argument with 'games'.

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