Our task in City Science is to create theories and models for what cities are, how they come to be, and the mechanisms and processes of their formation, maintenance, and decline. Urban Analytics then employs empirical data-driven methods to describe and analyse what is, and evaluate, test, and calibrate the theories and models. Together, they enable us to understand the physics, socioeconomics, and technologies of cities: their structure and form, of space and in space, the dynamics of flows and interactions within this form and space, and the entangled, interactional, morphological complexity of form/structure, behaviour, and function. But ultimately, cities are human agglomerations. The buildings, roads, urban spaces, and places exist to enable human interactions, whether these be social, economic, technological, or some combinations of these. Cities are the physical home in which the historical, economic, and social is lived, achieved, and realised. The city is the infrastructural basis which enables social, economic, and technological interactions to be actuated.So far, our science has made tremendous advances to the point where it is able to describe what a city is, how it came to be. And it can do this to an unprecedented level of spatial and temporal detail, a task that would seem Herculean and impossible only a couple of decades ago (Batty, 2024). Nonetheless, the future of our science will rest on how well our science is able to tell us what a city should be. It is time for a phase shift to occur in our science, towards building a Normative Urban Science, which should be informed by but distinguished from a Positive Urban Science.So far, our modern urban science tends much more towards the positive of what is, and what can be, rather than the normative of what ought to be. But perhaps it is too simplistic to generalise this view? After all, one could argue that the modern discipline of urban planning owes its very existence and development to the normative concern of addressing poor conditions of health and hygiene in cities during the industrial revolution. At its very root, the act of doing architecture and planning is a normative actthe planner, designer, or architect is primarily interested in shaping the future of spaces, places, networks, and forms. So, the act of building cities is inherently an imaginative and inventive act, an act of design (Batty, 2024), whether actuated centrally through a single agent or in a more distributed way through millions of agents. The question is: does the act always derive from a normative basis of reasoning?