The reader may be inclined to wonder why he is invited to consider such a wholly imaginary situation rather than the more familiar world of his experience. This procedure, I believe, is amply justified. By assuming that there exists an Authority furnished with all necessary knowledge, and able to implement its decisions as by the waving of a wand, attention can first be focussed exclusively on the logic of choice, as contrasted with all problems of information and practicability. Our approach will enable us to identify the criteria of efficient resource allocation; it will lead us, more directly than might at first appear, to an understanding of the problems which are common to all economic systems, and it will arm us with a set of ideas, or mental equipment, without which we could scarcely hope to deal with the more realistic issues which will confront us later. For these reasons the reader is asked to curb his impatience with what must inevitably be a highly abstract, and an intricate, line of argument. I shall fully recognize, in due course, that, as the real

world lacks the benefit-if so it be-of an omniscient Authority, economic decisions have to be taken by human beings, numerous and imperfectly informed.