INTRODUCTION

A successful research programme bustles with activity. There are always dozens of puzzles to be solved and technical questions to be answered; even if some of these – inevitably – are the programme's own creation. But this self-propelling force of the programme may carry away the research workers and cause them to forget about the problem background. They tend not to ask any more to what degree they have solved the original problem, to what degree they gave up basic positions in order to cope with the internal technical difficulties. Although they may travel away from the original problem with enormous speed, they do not notice it. Problemshifts of this kind may invest research programmes with a remarkable tenacity in digesting and surviving almost any criticism.

Now problemshifts are regular bedfellows of problem solving and especially of research programmes. One frequently solves very different problems from those which one has set out to solve. One may solve a more interesting problem than the original one. In such cases we may talk about a ‘progressive problemshift.’ But one may solve some problems less interesting than the original one; indeed, in extreme cases, one may end up with solving (or trying to solve) no other problems but those which one has oneself created while trying to solve the original problem. In such cases we may talk about a ‘degenerating problemshift’.

I think that it can do only good if one occasionally stops problemsolving, and tries to recapitulate the problem background and assess the problemshift.