The analysis of the trading networks fits in the comparative history of the world advocated by Fernand Braudel. The unity of the worlds considered (such as the Mediterranean for instance) does not depend on the geomorphic factors, but on the peoples who tie separate regions together. The motivation of these people comes from trade. But what is the nature of these commercial networks? How do they work and interact with the other components of the economy?
The problem of pre-modern long distance trade was that merchants had to rely on agents in the places they couldn’t be themselves. But, then, how to be sure of the honesty of this agent, as no state was involved to enforce the merchants’ codes of conduct? The answer brought to this question by the various merchant networks shaped their features and, ultimately decieded of their success or failure.
It is important to avoid the teleological trap that consists of overstating the significance of these networks in the rise of Europe and the Western culture. Two historiographies have been dealing with the question of the networks: the anthropological one, assuming that the economic activities of the networks depended entirely on cultural matters, and the functionalist one, stating that the rationality sustaining the networks was entirely economic.
It is impossible to understand the merchant network only in economic terms; they have important cultural sides. The most important value for the merchant was reputation. Indeed, the whole system was based on interdependency and reciprocity. Trust needed to be sustained by practices such as gifts, marriages and compadrazo (godfatherhood).
Several questions ought to be asked in the analysis of these networks: are they really as homogenous are they were said to be? How did they manage the necessary interaction with other networks?
Moreover, being far from the state’s power wasn’t necessarily a bad thing for the merchants. For instance, the Portuguese traders ill-treated in the fatherland managed, in the colonies, to lead jointly successful carriers in local politics and their commerce .
Besides, how did a network started? How was it able to settle in a given territory? Each one of them was very peculiar. While the English used proudly their flag as often as possible, their Greek partners, in the 17th century, tried their very best to reach a statute of “collective invisibility” (p.577). The features of these groups were complex and regularly changed. Thus, if successful, closed diasporas could drop their “tribal grammar” (Avrom Udovitch) and open to new partners.
On the long run groups tended to grow increasingly specialized (diamonds, wines…) and to construct a sophisticated division of labour. The authors hypothesize that the closed a network was around its religious, familial or else identity the most diversified it was. Consequently, the more heterogeneous a group was, the more specialized it got. Ultimately, this evolution would lead the liberalization of exchanges and the abandon of closed merchant networks. This is consistent with the theory of the weak tie . Open networks multiply the possible transactions, while, by their very nature, close networks limited them.
The authors expect the next researches to be directed towards a conceptualization of what was a merchant network and the unification of the various present current within one.
 PEDREIRA Jorge M. (2001) “Negócio e espaço social em Portugal e no Brasil (séculos XVII e XVIII)”, Penélope. Revista de História e Ciências Sociais.
 GRANOVETTER Mark (1983) “The Strength of Weak Ties: A Network Theory Revisited”, Sociological Theory, 1, 201-233