Judgement, truth and probability:
taste, (dis)agreement and compromise
Robin Cooper
University of Gothenburg
There is a considerable literature on exchanges such as the following
A: This soup tastes great
B: No, it's horrible
What are A and B disagreeing about? What, if anything, gets entered
onto A's and B's dialogue gameboards as a commitment resulting from
this exchange? A standard approach to these cases is to start from a
notion of proposition defined in terms of truth in possible worlds and
relativize this notion in some way to context possibly involving A's
and B's beliefs.
We will try to argue instead that we should turn this around: we start
from a notion of judgement, taking our inspiration from type theory.
An assertion represents our judgement about a situation being of a
certain type. In a large number of cases there is, in addition to
this judgement by an agent, also a putative fact of the matter: the
situation actually is, or is not, of the type. When there is a fact
of the matter a view of this can be entered as a commitment on the
gameboard. Otherwise, we can only enter information about the
judgement.
Some support for this view perhaps comes from hybrid cases where the issue of
whether there is a fact of the matter is unclear.
A: This milk is sour
B: I'm not so sure
There is arguably a fact of the matter as to whether the milk is sour
- on the other hand people's tolerance for sour milk varies and milk
is sour to a varying degree. This suggests a probabilistic or
gradient view of judgements of whether the milk is sour with different
thresholds of sourness being used by different agents.
Consider dialogues involving epistemic modals:
A: Sam might have arrived in Paris by now
B: She must have
A: Sam must have arrived in Paris by now
B: She might have
Are A and B agreeing or disagreeing and what should be entered as a
commitment on the gameboard? It seems that they are in partial
agreement, a compromise. If we treat epistemic modals in terms of
probabilities as has recently been suggested by Lassiter and Goodman
then it seems natural to say that the shared commitment is to the
lower probability of Sam having arrived in Paris. It is perhaps not
so obvious what the shared commitment should be if we take them to be
sets of possible worlds where A and B have different accessibility
relations.
Our proposal is therefore that we should analyze these examples using
a probabilistic type theory which builds on a notion of individual judgements.