James Dormer was an all-round merchant living in the first half of the eighteenth century. His main occupation was the trade in diamonds, and he managed to become involved in a circuit of traders that had different backgrounds. He worked on a reciprocal and regular basis with Jewish businessmen in London and Amsterdam, Brabant traders in Antwerp, French Huguenots in Lisbon and Protestants and Catholics in Holland. In analysing their daily operations as well as the underlying structures that made a regular and stable trade possible, the example of Dormer and his partners shows the relevance for a socio-cultural economic analysis. This network was constructed out of a search for profit, and as was the case for all trade, the self-interest of individual network members played a role. This did not mean that egoistic behaviour was sufficient to ensure a smooth series of transactions that were mutually satisfying. Traders relied on a series of mechanisms applied in their mutual correspondence to build trust between each other. It relied on personal reputation, and information regarding this commercial characteristic was divulged in trade letters. This led to a form of cohesion within the informal trade circuit of which Dormer was a part, but also connected merchants to a larger commercial society. Reputation was a negotiable commodity that circulated within this informal society and it was based on past conduct, judgement from others and creditworthiness.