The article suggests that the misuse of architectural form is the major threat to our cities. Form has power and form used mindlessly has indiscriminate consequences for the urban environment and its citizens.

To explore this ‘silent’ power of form, the article takes Louis Kahn’s lecture on ‘Silence and Light’ as its opening text. Kahn‘s distinction between the ‘measurable’ and ‘unmeasurable’ dimensions of architecture is compared to similar distinctions made by Kant, and extended by Schopenhauer at the turn of the nineteenth century. We learn that it is the ‘unmeasurable’ aspect of reality that gives form its power and in the second part of the article, using detailed analyses of Frank Lloyd Wright’s work, we are able to explain how the ‘unmeasurable’ is revealed within the ‘measurable’ and how such carefully balanced use of form can make a significant contribution to the health of our cities.