The COVID-19 pandemic necessitated social distancing at every level of society, including universities and research institutes, raising essential questions concerning the continuing importance of physical proximity for scientific and scholarly advance. Using customized author surveys about the intellectual influence of referenced work on scientists' own papers, combined with precise measures of geographical and semantic distance between focal and referenced works, we find that being at the same institution is strongly associated with intellectual influence on scientists' and scholars' published work. However, this influence increases with intellectual distance: the more different the referenced work done by colleagues at one's institution, the more influential it is on one's own. Universities worldwide constitute places where people doing very different work engage in sustained interactions through departments, committees, seminars, and communities. These interactions come to uniquely influence their published research, suggesting the need to replace rather than displace diverse engagements for sustainable advance.