Our profession is concerned with three "aspects of the world". First, how people behave when they feel a need for information; second, characteristic… - Brian Campbell Vickery

There is as yet no unified theory of retrieval systems, and a good deal of retrieval practice is still an empirical art, unsullied by theory.

Four years ago, when the first edition of this book was written, information retrieval was beginning to crystallize out as a unified discipline. The process has gone further today. Several other books... have also offered a general survey, although each has contributed its own special emphasis. Many conferences on the subject have been held, and a constant stream of new articles has appeared, both in documentation journals and in those in the data processing field. Information retrieval is now recognized as a discipline, and further advances in theory are being made, What I described in the first edition as the key operation in retrieval — the subject description of documents — is being explored theoretically and experimentally, although we are still a long way from reducing this operation to rule (Chapter 3). There has been less new work on the design of descriptor languages, although ideas on the display of descriptor relations through thesauri and 'semantic maps' have been developed (Chapter 4). Access to files has been examined, particularly by those experienced in data processing.

John Desmond Bernal (1901-1971) was undoubtedly the most important of the "Western" scientists who, during the twentieth century, accepted the Marxist view of social development. He did more than "accept" it: he tried to sketch the whole history of science from a Marxist viewpoint; he wrote a number of articles explicitly expounding his view of the relation of Marxism to science; and from his student days he played an active role in Communist politics. He has been criticised: during his lifetime, for too readily accepting official Soviet policy, whether relating to society or to science; since his death, for having been too ready to hope that his vision of the use of science for human ends could be implemented by capitalist societies; and at all times, for an allegedly simplistic faith in science as the salvation of mankind.