The problem I want to discuss might be put, first of all, like this: How can architects and planners build for the future when they happen to be imprisoned — for lack of what H. G. Wells would call a "time machine" — in the present? The future is open; we do not know what it will bring. Yet, "planners have to imagine the future as a matter of routine. Whether you are building a motorway, a chemical works or a school, you are making a forecast of the continuing need for such a thing over its economic life."¹