National foreign policies, however complex the forces which go to their making, live and operate within the context of their time. Those who shape and apply policy must needs display a perceptive awareness of the essential characteristics of the international framework of the day, since those characteristics will not only prescribe the mode of procedure but also determine the limits to possible achievement. Change is of the essence of history, and international relations are no more immune from the process than other forms of human activity. This imposes on those who make decisions, and hopefully upon the communities concerned, a responsibility for detecting not simply the alchemy of change but the nature of the forces which will transmute the features dominant in one period into those dominant in the next.