The key contribution of this article is its articulation of a conceptual framework for understanding the function and foundations of urban tolerance. The function of tolerance is defined as the capacity of the citizenry to negotiate harmonious encounters with difference and to engage with difference to secure improvements to social well-being. Yet the populations of cities are increasingly disconnected, spatially and socially. Has the citizenry lost its capacity, or indeed its willingness, to encounter and engage with difference? Strategies that endeavour to impose a mode of social interaction, which treat difference as illegitimate and understand tolerance as static, run the risk of perpetuating a cycle of intolerance. In contrast, the existence of a shared language of social interaction and the recognition of the legitimacy of difference are defined as the interrelated foundations of tolerance. Strategies to accommodate difference that appreciate the dynamism of tolerance, can unlock the potential of the citizenry to encounter and engage with difference.