Agent-based modelling (ABM) is becoming more prominent in the social sciences. However, ABM has not often been used in legal studies even though this method offers promising perspectives, also for legal-historical research. ABM is involved with interactions and the combined results of interactions over time. ABM starts from a simulation of a complex reality and provides handles to interpret dynamic processes of change. Changes are expressed as the combined result of agents’ behavior, or changes of their features, in response to constraints, incentives and the actions of other agents addressing those constraints and incentives. ABM is apt for social sciences because it allows to capture feedback loops. The choices made by agents can affect variables, thus triggering new behavior. In addition, ABM facilitates the testing of variables that intersect as well as their relative weight in the patterns that emerge.
In a new research project I intend to analyze the development of the meaning of sovereignty concepts in the period 1400-1620, within the context of trade and cities of commerce. I have found out that in the mentioned period the sovereignty of commercial centers was expressed with many different concepts and that they could develop new meanings. Concepts of sovereignty could come to reflect both domestic and international settings with regard to trade. For example, in the fourteenth century the city of Antwerp was legally considered a “libertas”. This notion referred to the charter of the Duke of Brabant of 1221, which bestowed upon the Antwerp aldermen the right to issue bylaws and to impose judgments within the city and a small region surrounding it. This territorial jurisdiction was referred to as the “libertas of Antwerp”, and often in combination with a reference to its fortress. The “libertas castrensis” was the area in which the Antwerp aldermen had judicial competences; in times of military occupation the inhabitants of this territory could seek shelter in the Antwerp stronghold. However, in the second and third quarter of the sixteenth century, the city of Antwerp was depicted as a “libertas”, in the sense of a merchant republic. By that time the notion of “libertas” expressed the idea that trade brought affluence to the city and that there was a municipal government that ruled fairly, taking the interests of trade and foreign merchants into account. Clearly, the change of meaning of the sovereignty concept was rooted in the economic changes the city of Antwerp had witnessed between the fourteenth and sixteenth centuries. Other sovereignty concepts continued to be used as well. Communitas, for example, evolved from a notion expressing dependence on the ducal authority to a more independent concept of autarkic community.
Urban republicanism provided an underpinning for lobbying efforts and autonomous diplomatic action. For example, in 1549 Cornelis Grapheus, the secretary of the city, prepared a sophisticated public-relations campaign that was set up for inaugurating prince Philip, later Philip II, as margrave of Antwerp. In 1549, Charles V introduced his son to the Low Countries as future heir and the city of Antwerp took the opportunity to show off its riches in a ceremony that involved depictions and theatrical scenes throughout the city. The prince was guided to different locations where arches had been erected, mentioning phrases that lauded the sovereign’s authority but which at the same time mentioned the powers of the city as well. The concept of the Antwerp republic was promoted. The public events came after a period of backdoor politics; in the months preceding the Joyous Entry the administrators of the city of Antwerp had negotiated over new privileges and in their requests the same strategy of emphasizing the powers of the prince and of the city, as an economic respublica, had been used.
Antwerp in 1598
All this was more than rhetoric. In fact, a few years before, the Antwerp aldermen had started a policy of independent trade negotiations, without consulting the monarch. In 1546 the Antwerp pensionary Jacob Maes had travelled to Lübeck and had agreed on a treaty with the aldermen of that city, and also the Hansa Diet. The privileges that were agreed on were in part to be confirmed by the Duke of Brabant, in part they were exclusive agreements between Antwerp and the Hanseatic authorities. This was remarkable; an Antwerp official signed a treaty that was partially to be confirmed by the princely institutions, which were not aware of the negotiations that had resulted in the agreement. This clearly demonstrates that the economic power of Antwerp transpired into the area of international politics; the Hanseatic authorities considered Antwerp as a sovereign polity. In February 1546, the agreement between representatives of the Hansa and the Antwerp aldermen was made public at Antwerp, in the form of a municipal bylaw, to which also 22 articles were added for which confirmation would be sought from the central authorities. The parts that were sent over to the Duke for corroboration were concerned with tolls and saufconduite; in the parts of the agreement with Antwerp alone much emphasis was laid on the jurisdiction of the Antwerp aldermen. However, for some articles, referring to criminal jurisdiction, the écoutète, who was the representative of the Duke at Antwerp, was implied as well. Therefore, also for those points of the treaty that the Antwerp administrators considered as referring to their competences only, there was a clear connection to the princely authority as well.
Here below goes a piece of code, written for the software package of NetLogo. This software allows for running simulations that aim to explain how sovereignty concepts change in reference to dynamic processes within a city. Such simulations must encompass several subsystems, including merchants, intellectuals and craft guilds. The idea is that within these subsystems interactions happen that are independent from developments in other subsystems, but which nonetheless produce outcomes that have an impact on the simulation at large. The excerpt of code refers to a subsystem of merchants and programs the part of the simulation that demonstrates their interactions in reference to sovereignty concepts. The programming is such that sovereignty concepts evolve from a traditional to a more economic meaning over time. This is written in the code in such a way that with the passing of time more merchants arrive in the urban market and that initially they have a preference for “economic” sovereignty concepts. However, individual merchants accumulating wealth have an incentive to change this preference once they have gathered enough means to be eligible to participate in the city’s governmental institutions. They then choose more traditional sovereignty concepts to depict the city's jurisdiction or clout. This follows from the assumption that participation in political structures requires more conforming to traditional standards. ABM is useful to detect what happens with variables that at first sight yield conflicting results. This is also integrated into the code of the example. If the number of merchants rises, the individual wealth of merchants declines. But rising average wealth attracts more merchants. Moreover, there are several feedback loops in the code. High levels of wealth both stimulate “economic” sovereignty approaches, but also curtail them. Once merchants gather more wealth, new merchants are drawn to the city's market, and they opt for economically orientated sovereignty concepts. But - as mentioned - sovereignty concepts can become more traditional as well. In that case the average wealth declines (this is programmed such that all merchants lose a part of their assets; poorer merchants are affected more than wealthier ones) and smaller merchants disappear. When the model is run, more and more sovereignty concepts will emerge (they do not disappear when the merchants chosing them disappear); the outcome is a certain number of concepts of a certain colour (traditional: darker green, economic: lighter green).
Preliminary runs of this model have been tested; the datalogs derived from the model runs are currently being analyzed and the plan is to write an article on those, which will then – hopefully – contribute to further exploration of the method of ABM by legal (and economic) historians.
Bibliography
De ruysscher, D., “Lobbyen, vleien en herinneren: vergeefs onderhandelen om privileges bij de Blijde Inkomst van Filips in Antwerpen (1549)”, Noord-Brabants Historisch Jaarboek 29 (2012), 64-79.
De ruysscher, D., “Mercantile Jurisdiction and Sovereignty: The City of Antwerp versus the German Hansa (16th Century)”, in the press.
Chittolini, G., L’Italia delle civitates, Turin, Giapicchelli, 2015.
Namatame, A.K. and Chen, S.-H., Agent-Based Modeling and Network Dynamics, Oxford, Oxford University Press, 2016.