How do you think through influence when you are a historian in the 1970s ? That is the question considered in this article, on the basis of Carlo Ginzburg’s book, The Cheese and the Worms, which explores the origins of a 16th century miller’s unique ideas. A certain tension is detected in the understanding of these origins, which rejects the model whereby books exert a direct influence, while at the same time recognising their role in generating thought. Influence, therefore, is no longer seen as a matter of cause or determination, but one of encounter.