Program
Invited speakers
- Guillaume Aucher, University of Luxembourg
- Alexandru Baltag, Oxford University
- Johan van Benthem, University of Amsterdam and Stanford University
- Guido Boella, University of Turin
- Dov Gabbay, King's College London and University of Luxembourg
- Davide Grossi, University of Amsterdam
- Emiliano Lorini, Universite' Paul Sabatier
- Gabriella Pigozzi, University of Luxembourg
- Henry Prakken, Utrecht University and University of Groningen
- Antonino Rotolo, University of Bologna
- Paolo Turrini, Utrecht University
- Emil Weydert and Richard Booth, University of Luxembourg
Schedule
Abstracts
Distinguishing norm change from information change (Guillaume Aucher, University of Luxembourg) Slides
Normative sentences can be used to change or to describe the normative system, known
as prescriptive and descriptive obligations respectively. In applications of deontic
logic, it is important to distinguish these two uses of normative sentences. In this
talk, I show how they can be distinguished and analysed in a dynamic epistemic
deontic logic. Observing that this logic only allows to specify norm promulgation, I
also propose another approach where norm derogation can be modeled.
Dynamic-doxastic norms versus doxastic-norm dynamics (Alexandru Baltag, Oxford University) Slides
In addition to doxastic norms (e.g. educated people in the 21st
century should believe in Evolution), there also exist norms for
doxastic change (e.g. Catholics should accept as infallible the
Pope's pronouncements, i.e. always perform a hard belief update with
whatever the Pope announces). Some of these ``dynamic-doxastic
norms" may be thought to correspond to (some of) the various belief-
upgrading procedures proposed in the literature (Bayesian or Jeffrey
conditionalization, radical belief upgrade, conservative upgrade
etc) . Different paradigms may be embodied in different such norms
for belief revision: e.g. the AGM approach prescribes always
accepting the new information while minimizing the resulting belief
change as much as possible; a fundamentalist's norms would prescribe
keeping the old beliefs no matter what; while Learning Theory
prescribes adopting the revision procedure that is most likely to
lead faster to ``the truth". Specific events (religious conversion
or apostasy, loss of trust in a person, hard evidence or even simple
logical reasoning) may prompt one to revise his/her very norms for
belief revision. I give some examples in this sense, including the
Surprise Examination Paradox, and I discuss the possibility of
formalizing these meta-changes, as a first step towards a future
``Revision Theory of Belief-Revision Norms".
A Dynamic Logician Looks at Deontics (Johan van Benthem, Universities of Amsterdam and Stanford)
Deontic reasoning is an exciting mixture of information
about people and the world, and evaluation of what our
actions achieve there. I will present some dynamic logics
that put information and evaluation on an equal footing,
and then discuss [some feasible sample of] what they
suggest about * changing obligations and changing norms,
* mixed semantic-syntactic representations, and obligations
having to do with both (e.g., process duties of reasoning well),
* entanglements of obligation and information, and some
parallels with other areas where this phenomenon plays,
* game perspectives and group obligations. My main
purpose is to explore what old issues will look like,
and have an agenda discussion between communities.
Lex minus dixit quam voluit, lex magis dixit quam voluit: norm change for legal
interpretation
(Guido Boella, University of Turin) Slides
This talk proposes a logical framework which is able to capture
the norm change power and at the same time the limitations of the judicial system in
revising the set of constitutive rules defining the concepts on which the
applicability of norms is based. In particular, the framework is used to reconstruct
some interpretive arguments described in legal theory such as those corresponding to
the Roman maxims
General Norm Change
(Emile Weydert and Richard Booth, University of Luxembourg) Slides
In this talk, we are going to sketch a general framework for norm change which
tries to take into account some specificities of norms and their dynamics as
compared to assertions and belief revision. We see norms as inferentially inert
conditionals, to be distinguished from conditional obligations. Normative states or
systems are structures reflecting the history of norms as well as their status. This
information and the logical structure of norms will guide the revision process
initiated by the creation or reaffirmation of norms. We illustrate the approach with
a simple norm change strategy reflecting the specific nature of norms. We also make
some remarks about its relation with belief change.
Reactive Theories and Norm Change (Dov Gabbay, King's College London) Slides, Abstract
Voluntas bonorum consonat legi: The two faces of betterness (Davide Grossi, University of Amsterdam) Slides
In this talk I will look at deontic logic as resulting from both a betterness
ordering on states and a betterness ordering on propositions. The correspondence
between these two orderings offers a rich perspective from which to look at deontic
scenarios. I will then present some preliminary work on the types of dynamics that
can be captured within such a framework.
The logic of acceptance: a bottom-up perspective on institutional reality (Emiliano Lorini, Universite' Paul Sabatier) Slides
The topic of this talk is the logic of acceptance, a modal logic
framework recently proposed in the domain of multi-agent systems, which
allows to express what certain agents accept while functioning together as
members of an institution, and to ground the abstract level of
institutions on agents' mental attitudes.
I will first present the static logical framework by showing how several
normative concepts (e.g. obligations, permissions, constitutive rules,
social commitments) can be defined in the acceptance logic.
Then, I will present some recent developments of acceptance logic which
have been proposed in order to deal with institutional dynamics. I will
provide a formal semantics and complete axiomatization of three basic
operations on acceptance: announcement in an institutional context,
acceptance shift, assignment on acceptances. The first operation allows to
formalize the act of issuing a norm in an institution and its effects on
the acceptances of the institution members. The second operation is a form
of revision operation for acceptance which allows to model a radical
change in an institution and a process of institution formation. The third
operation will be used in order to characterize the dynamics of social
commitments (commitment creation and commitment cancelation).
In the last part of the talk, I will shed light on the logical distinction
between the concept of acceptance, and the classical concepts of belief,
common belief and preference which have been extensively studied in the
philosophical literature and in the area of multi-agent systems. I will
offer some perspectives for an extension of acceptance logic by doxastic
modalities and modalities for preference.
What is norm change?
(Gabriella Pigozzi and Leon van der Torre, University of Luxembourg) Slides
In this talk we give a historical survey on norm change, we present some
benchmark examples, and we distinguish it from the dynamics of obligations and
permissions over time.
On norms for the dynamics of argumentative interaction: argumentation as a game
(Henry Prakken, Utrecht University)Slides
Argumentation is one of the hot topics in current logic-based AI research.
It is studied both as a form of (nonmonotonic) inference and as a kind of
interaction between rational agents. In this \'a0talk the modelling of
argumentation in both senses as a kind of game is discussed. My main claim
will be that the rules of the game, or norms, for argumentation-based
inference are fundamentally different from the norms of argumentative
interaction: while the former derive their justification from semantic
accounts of nonmonotonic inference, the latter are instead meant to
promote fair and effective conflict resolution.
Modeling Legal Dynamics in Defeasible Logic
(Antonino Rotolo, University of Bologna)Slides
The law implements norm dynamics through different types of
legal modifications. Basically, modifications can be either explicit
or implicit. In the first case, the law introduces norms whose
peculiar objective is to change the system by specifying what and how
other existing norms should be modified. In the second case, the legal
system is revised by introducing new norms which are not specifically
meant to modify previous norms, but which change in fact the system
because they are incompatible with such existing norms and prevail
over them. In this talk I will report on my recent research into using
suitable extensions of Defeasible Logic (DL) for modeling explicit
modifications. I will first discuss some relevant types of
modifications, such as those which concern the text of legal
provisions, their validity and existence, their scope, or their time
of force, efficacy, or applicability. Second, I will consider when
ideas and techniques from belief and base revision can be applied in
DL to capture these modifications and when legal dynamics require to
resort to richer languages and logical tools, such as the ones
provided by some temporal extensions of DL.
Expressing obligations by strategic ability update
Paolo Turrini (Utrecht University)Slides
The presentation will concern the interaction properties between preferences
and strategic ability (a set of choices, i.e. a set of sets of
alternatives) of coalitions (a set of players).
A language will be introduced to talk about the conflict between
coalitionally optimal and socially optimal choices.
Optimality of choice will be described taking into account the
modifications (updates) of a coalition's strategic ability induced by the
possible decisions taken by the other players. Obligations will be seen as
constructs that enable to identify socially optimal choices. To formalize
them a semantics for strategic ability update will be discussed.
The workshop is held under the auspices of
