TributesI have been particularly impressed by the courageous and penetrating attempts which Constantinos Doxiadis has made to lay a theoretical foundation for a science of ekistics. Only the very best of practical men - builders, as he calls them - become deeply enough involved with the matters they deal with to feel the need of passing beyond an intuitive understanding based on experience to one founded on intellectual under-standing. It is enormously difficult to create such a structure of theory in a subject so complex as human settlements. Nobody who was not as bold and original as Dinos would have dared to try it. He would probably be the first to admit that he has not completed the task; but he should know how grateful his friends are that he has started on the task, and how much they are impressed by what he has already accomplished. May he long continue!