The third lecture analyzes the possibility of gaining mutual understanding between culturally different groups of people, a foundational challenge to education in a globalized world. Cognitive models of intersubjective understanding, such as Herbert Clark’s theory of ‘common ground’, emphasize the mental and discursive aspects of mutual understanding. The lecture argues that this is not enough; focus needs to be shifted to the role and potential of shared material objects as sources of intersubjective understanding. ‘Common ground’ needs to be reconceptualized in terms of real objects between the subjects. The lecture analyzes the formation of materially based common ground between two groups of builders of wooden boats, one located at the Bay of Bengal in India, the other one in Helsinki, Finland. The two groups have radically different educational and cultural backgrounds, they use very different tools and their boats are built for different purposes. The builders were asked to look at photos of the other boat building site and comment on them. Our analysis shows that they began to build mutual understanding by focusing on their shared object, the wooden boat. Common ground emerges as the generalized material object between the two groups, constructed by means of identifying salient differences, dimensions of difference, questions, comments on relationships, and comments on historical conditions.