If industrial cities have a finite capacity for growth, beyond which they cannot sustain viable behaviour, and we can find out what it is, then we would have a way of appraising their prospects of continued development. We would also be able to predict the overall incremental effects of growth and perhaps be able to judge when we should rein in settlement growth or change the density trajectories of our cities to avoid adverse behavioural effects. A predictive model of the behavioural limits on viable community life set by settlement area and residential density should therefore be of some relevance, especially for analyses of the potential impact of urban development. An operational uniformitarian proposition is required which specifies the relationship between the behavioural boundary conditions and the consequences of approaching them. To assess such a model a time-scaled perspective is required which will allow us to identify the rates of change associated with the long-term boundary conditions which constrain viable community life in human societies.