This volume, by two of the profession's most eminent monetarist economists, offers a unique perspective on a key issue of monetary economics: the effect of money on output. Karl Brunner and Allan Meltzer address the theoretical aspects of this issue with the purpose of understanding their policy implications. The opening lecture offers an historical overview of the relationship between money and output. The second lecture presents their well-known model of a monetary economy. The real sector, and in particular the government budget constraint, is examined in the third lecture. The Leitmotif of the lectures, uncertainty and the costs of acquiring information is the theme of the final lecture. Here they argue that uncertainty can be most effectively reduced by relying on rules rather than discretion, and by basing rules on observation rather than on forecasts.