Note: Předneseno na společném kolokviu Humboldtovy nadace a Ústavu pro pokročilá studia v Princetonu 24. 8. 1981. Poprvé publikováno v Proceedings of the Bi-National Colloquium of the Alexander von Humboldt Foundation at the Institute for Advanced Study. Přeložil O. Kowalski.

Note: Delivered at a colloquium - first published in Proceedings of the Bi-National Colloquium of the Alexander von Humboldt Foundation at the Institute for Advanced Study, Princeton, New Jersey, August 23—26, 1981.