# G.W. Leibniz Connections Between Law & Logic

**Programme de la conférence**

**Mardi, 12.11.2013**

Jusque 17 h – Arrivée des participants

18.00 h – Accueil à l'hôtel Barbarossa : dîner de bienvenu

**Mercredi, 13.11.2013** (WOBAK Haus, Benediktinerplatz 7)

09.00 h – Ouverture de la conférence par le Président du l'Université de Konstanz

09.30 h – Shahid Rahman: *“The Epistemic Role of Dependent-Evidence and the Notion of Conditional Right”*

10.30 h – Pause

11.00 h – Présentations et discussions

Alberto Artosi & Giovanni Sartor: *“The Logic of Perplexity. Leibniz on Hard Cases“*

Giuliano Bacigalupo: *“On the Retroaction of the Condition: Leibnizean Thoughts and Beyond”*

13.00 h – Repas

14.30 h – Présentations et discussions

Alexandre Thiercelin: *“On the Localization of Virtuality in the Law: Leibniz and the Existence of Conditional Rights”*

15.30 h – Pause

16.00 h – Présentations et discussions

Matthias Armgardt: *“Presumptions and Conjectures in Leibniz´ Legal Theory”*

Thomas Piecha:* “Closed Rule Systems”*

18.00 h – Discussion administrative : organisation et planification, poursuite et développement du projet

19h30 – Dîner Conférence et discussions Hexenküche, Konstanz

**Jeudi, 14.11.2013** (WOBAK Haus, Benediktinerplatz 7)

09.00 h – Présentations et discussions

Bettine Jankowski: *“Leibniz’ Third Rule of Perplexity for Circular Dispositions of Divisible Things”*

10.00 h – Pause

10.30 h – Présentations et discussions

Sébastien Magnier & Juliette Sénéchal: *“Suspensive Condition and Epistemic Dynamics: Past or Present Debates?”*

12.30 h – Mittagessen

14.00 h – Présentations et discussions

Karlheinz Hülser: *"Doors to ancient philosophy in the time of Leibniz"*

Juliele Sievers: *“Norms and Temporality**”*

16.00 h – Pause

16.30 h – Présentations et discussions

Juliana Albuquerque-Katz: *“Recognition and the Place of the Other”*

17.30 h – Bilan de la conférence

18.00 h, départ pour Fuchshof

19.00 h – Dîner Conférence et discussions Fuchshof, Oberdorf

**Vendredi, 15.11.2013**

A partir 10.00 h – Départ des participants

**Abstracts**

Shahid Rahman: *“The Epistemic Role of Dependent-Evidence and the Notion of Conditional Right”*

The main aim of the present paper is to study the notion of conditional right by means of constructive type theory (CTT) according to which propositions are sets, and proofs are elements. That a proposition is true means that the set has at least one element. The analysis of conditional norms should follow as a generalization the details of which are not the subject of the present paper. The CTT approach allows to formulate cases of conditional right such as *If A, then Secundus has the right to B, *as the hypothetical, *Secundus has the right to B, provided there is some evidence x of A. *Herewith I follow Thiercelin’s (2009, 2010) interpretation that makes of the notion of dependence the most salient logical characteristic of Leibniz’ approach to conditional right. Moreover, in line with Armgardt (2001, pp. 220-25) I will first study the general notion of dependence as triggered by hypotheticals and then the logical structure of dependence specific to conditional right. However, on my view, the dependence of the conditioned to the condition is defined on the pieces of evidence that support the truth of the hypothetical rather than on the propositions that constitute it. Accordingly, a basic form of conditional norm is constituted by a set and a proposition such that the set provides the conditions under which the proposition (that establishes the right) is made true. I will develop this idea in a dialogical frame where the distinction between *play-object* and *strategy-object* leads to the further distinction between two basic kinds of pieces of evidence. The proposed approach includes the study of *formation rules *that model the argumentation on the acceptance of a piece of evidence.

Alberto Artosi & Giovanni Sartor: *“The Logic of Perplexity. Leibniz on Hard Cases“*

In his 1666 doctoral dissertation *De casibus perplexis* (On Perplexing Cases) Leibniz undertook an overall approach to “perplexing” (i.e., hard) cases by providing (*i*) a definition of “perplexing case”; (*ii*) a classification of perplexing cases, and (*iii*) a set of decision rules for the solution of perplexing cases. This paper aims at providing a clear understanding of Leibniz’s approach to perplexing cases by focussing on the logical scheme behind their classification into (*a*) perplexing cases deriving from a self-contradictory or otherwise problematic legal act (“perplexing disposition”), and (*b*) perplexing cases deriving from conflicting priorities between several competing claimants (“perplexing concursus”).

Giuliano Bacigalupo: *“On the Retroaction of the Condition: Leibnizean Thoughts and Beyond”*

I start by presenting the standard approach to contracts with a suspensive (or resolutive) condition in Law: given a conditional contract with a suspensive (or resolutive) condition, the obligation goes into effect (or ceases to exist) when the condition is fulfilled (e.g. BGB § 158 I, Codice Civile 1353, Code Civile 1168). Next, I focus on how certain legal systems introduce the fiction of the retroaction of the condition to address, among others, the problem of *Zwischenverfügungen *(e.g. Code Civile 1179, Codice Civile 1360). Thirdly, I present an alternative approach to contracts with a suspensive (or resolutive) condition developed by Leibniz, which should render the fiction of retroaction superfluous. Finally, after having addressed some problems linked to Leibniz´ solution, I put forward an argument that may be used to come to the rescue of both the standard approach and the fiction sometimes linked to it.

Alexandre Thiercelin: *“On the Localization of Virtuality in the Law: Leibniz and the Existence of Conditional Rights”*

The conditional mechanism is not only a basic mechanism of everyday legal practice. It is a major mechanism of legal theory, too. Many legal mechanisms, in particular those in which virtuality is involved, are usually explained in terms of conditional rights. Such a reduction of virtuality to conditionality is not satisfactory because it tends to reduce conditional rights to virtual rights. In my talk I will show how Leibniz's theory on conditional rights proves the actual existence of conditional rights. That is, I will show how Leibniz localizes the virtuality displayed by the conditional mechanism. Nevertheless, it will not be possible not to mention some limits of Leibniz's localization in respect with some new trends in contemporary legal theory. As a result, I will plea for a pluralistic approach to virtuality in the Law in which conditionality is not all that can be said about legal virtuality.

Matthias Armgardt: *“Presumptions and Conjectures in Leibniz´ Legal Theory”*

We will analyse three texts of Leibniz dealing with presumptions and conjectures from various periods:

- Elementa Juris Naturalis (EJN), 1671

- De legum interpretatione, rationibus, applicatione, systemate, 1678/79

- Nouveaux Essais sur l’entendement humain, 1704 (published post mortem, 1765)

Thomas Piecha:* “Closed Rule Systems”*

We first give a brief overview on the ANR-DFG project "Hypothetical Reasoning". We then consider extensions of logic by systems of rules. Such rule systems might be used to represent systems of laws, for example. If a given rule system can be assumed to be closed, then a reflection principle becomes available, which can be used to reason about the given rule system. We show how the reflection principle enables us to infer hypothetical statements with respect to given closed rule systems, and how additional information can be extracted through variable bindings. Finally, we mention some results on extensions by closed rule systems.

Bettine Jankowski: *“Leibniz’ Third Rule of Perplexity for Circular Dispositions of Divisible Things”*

Leibniz separates perplex cases in different categories. For each category he lays out a rule that should cover all possible cases in this category. In this presentation I will concentrate on the third category of perplex cases: when more than two debtees have a claim on the same piece of property or inheritance etc. and the thing in question is divisible. Leibniz claims that in these cases the just or right solution is to satisfy each claim *pro rata. *I will examine what kind of cases fall into this category of perplexity as well as consider the rule and how it applies to the examples Leibniz offers. The main aim is to see whether Leibniz’ rule does apply to all such cases and can actually offer a feasible solution. A second focus is on the role of Saxon law as applied to these cases.

Sébastien Magnier & Juliette Sénéchal: *“Suspensive Condition and Epistemic Dynamics: Past or Present Debates?”*

Nowadays the suspensive condition is probably one of the most regularly used legal instruments in Law.In the French Law, it is commonly admitted that this kind of condition is a modality of an obligation: the existence of the obligation is dependent on the fulfillment of the condition. Nevertheless, some recent works based on Leibniz’s reflections about the suspensive condition invite us to reconsider not only the French conception of this particular notion of condition but also some contemporary projects of reform. What a surprise to discover that this notion leads to many pitfalls, regarding both its nature and its legal effects. All of these pitfalls give rise to many questions: Is suspensive condition a modality of an obligation or rather a modality of a legal act? If the suspensive condition must be uncertain, that uncertainty should be understood from an ontological or an epistemical point of view? If most of the time the Doctrine excludes past events as suspensive conditions, is this measure really convenient? When a condition is fulfilled, is there a retroactivity concerning its juridical effects? In this presentation we will investigate all of these questions, in order to propose a reformulation of both the definition of the suspensive condition and its legal effects.

Rainhard Bengez: *“Computable Legal Theory: Between Digital Machines and Specification, Presocratic’s Concept of Data and Leibniz’ Epistemology. A data type and syntax based approach to jurisprudence.*”

At its core Computable Legal Theory starts to identify and to make practical and theoretical use of computable structures and computable contents of jurisprudence (in a broader sense).On the one hand it takes the perspective of a digital machine and omits any kind of (logical or formal) framework not working tight with an actual machine model. More formally spoken it is more related to a logical and data type based interpretation of intuitionism. This syntactical or data type based approach makes it unique among other theories concerning legal theory, AI and law, or legal logic and legal philosophy. It is different from any kind of computational legal theory as it doesn’t aim at formalizing things in terms of set theory or pre-set-theory. Not the model is important but its computable content and structure. And this is not just a pure play-around with words as many of the models provided yet are fare away from being useful for any practical purposes and also not useful because its lack of computability. Of course, besides a pure data type oriented logic there is a semantic way (in a logical sense) expressing computable contents e.g. by formulating algorithms. On the one hand CLT provides a strong typed logical framework based on data types and is helpful in finding useful algorithms for legal informatics but requires a different prospective on jurisprudence. On the other hand it needs a better philosophical grounding.

In this talk we are aiming at drawing the development of the concept of data in pre-Socratic philosophy and its extension in Leibniz’ epistemology in which he makes extensive use of organized units (monades); something which can be interpreted as data types and a kind of pre-(data)-typed logic. Besides our grounding effort we want to introduce some of the advantages of CLT.

*Juliele Sievers: ** “Norms and Temporality”*

Normally, the main context giving rise to questions concerning the temporal aspect in Law are the ones involving cases of conflicting norms. To Kelsen, situations of norms in conflict must be resolved not via the application of logical principles, namely the principle of non-contradiction, and not even by traditional legal principles such as *lex posterior derogat priori*, but rather by the application of a special kind of legal norm itself, called derogating norm. The purpose of this presentation is to give an overall view of how norms relate to the temporal aspect in the kelsenian positivistic theory, namely how a norm “exists” in time, and how it can lose its validity over time. We will also analyze the question of retroactivity, and the question of the lacking of efficacy after a determined period of time and how it affects the losing of legal validity. Lastly, we aim to investigate how fictions, such as the Basic Norm, relate to time according to Kelsen’s theory. All these elements will help us to better understand how central the temporal aspect is and how deeply it affects the legal validity in Kelsen’s theory. The conclusions drawn in these investigations might serve as a frame of comparison in relation to Leibniz’ Natural Law tradition, mainly in problems related to legal conditions and their temporal features.

Juliana Albuquerque-Katz: *“Recognition and the Place of the Other”*

The problem of the other as related to the self is a philosophical issue that interests both Leibniz and Hegel, giving shape to both their metaphysics and their ethics. Thus, in this presentation, I have chosen to investigate how their thoughts about the relation between otherness and selfhood can help us think about an ethics based upon the map of intersubjective relations and the use of communication in order to forge the expression and maintenance of our individual freedom. All through this investigation my goal is to provide a key to the revitalization of the Leibnizian argument. Therefore, I will adapt it to some of the present discussion in political philosophy and ask how the Place of the Other could interact and enrich the debate about the notion of recognition.