This chapter demonstrates that identity-related connections that consumers form with possessions profoundly affect judgment and behavior. The authors first outline the implications of ownership for product-relevant domains from the lens of egocentric categorization theory (ECT). ECT explains when and how: (1) the material environment affects consumer judgments and decisions about the self; and (2) the self affects judgments and decisions about material objects. According to ECT, consumers categorize products relative to the self, based on ownership. Consumers then judge the self in assimilation or contrast to material objects, as well as judge material objects in assimilation or contrast to the self. The authors then describe the “see-saw self” model that highlights the implications of ownership for product-irrelevant domains: Product ownership not only affects identity behavior in product-relevant domains, but also deactivates identities in product-irrelevant domains. This identity-deactivation results in impaired performance on tasks in product-irrelevant domains. The authors propose avenues for future identity research.