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Abstract:

This paper is a contribution to the formalisation of Thagard’s coherence theory. The term coherence
is de?ned as the quality or the state of cohering, especially a logical, orderly, and aesthetically
consistent relationship of parts. Cognitive coherence in particular is the coherence theory based
explanation of the mind which evaluates the truth of a cognition in terms of it being a member of
some suitably de?ned body of other cognitions: a body that is consistent, coherent, and possibly
endowed with other virtues, provided these are not de?ned in terms of truth. Thus a coherent set is
interdependent such that every element in it contributes to the coherence. We take the Thagard’s
proposal of a coherence set as that of maximizing satisfaction of constraints between elements and
explore its use in normative multiagent systems. In particular we show how it could be used as a
mechanism to introduce true autonomy in agents particularly in a normative multi agent setting.
We show, how an agent can deliberate on norm evaluation while also considering other factors such
as sanctions and rewards.
We ?rst provide a general coherence framework with the necessary computing tools. Later we
introduce a proof-theoretic characterization of a particular type of coherence namely the deductive
coherence based on Thagard’s principles, and derive a mechanism to compute coherence values
between elements in a deductive coherence graph, thus proposing a fully computational model of
coherence. Our use of graded logic helps us to incorporate reasoning under uncertainty which is more
realistic in the context of multiagent systems. We then explore a scenario where agents deliberate
about norm evaluation in a multiagent system where there is competition for a common resource.
We show how a coherence maximising agent decides to violate a norm guided by its coherence.

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