The inherent difficulty of heuristics, the study of design method, is that one becomes fascinated by means, rather than with ends. One tends to think of "problem-solving" instead of "design" and to concern oneself with rational procedures instead of creative acts. All design processes are based on scientific method. For some time now, the aim has been to devise rationalized procedures analogous to the mathematician's algorithm, sets of instructions for solving particular problem types which require no access of creative thinking whatsoever. Some theorists such as Davis (1958) have suggested that if no such algorithm exists, then the problem is unsolvable. As Gosling (1963) has pointed out, design methods have their vogue and then fall from esteem. If they really are of value, their development is continued into a specialized branch of knowledge, which will then be useful in the understanding of particular classes of problems.