INTRODUCTION

Popper's ideas represent the most important development in the philosophy of the twentieth century; an achievement in the tradition – and on the level – of Hume, Kant, or Whewell. Personally, my debt to him is immeasurable: more than anyone else, he changed my life. I was nearly forty when I got into the magnetic field of his intellect. His philosophy helped me to make a final break with the Hegelian outlook which I had held for nearly twenty years. And, more important, it provided me with an immensely fertile range of problems, indeed, with a veritable research programme. Work on a research programme is, of course, a critical affair, and it is no wonder that my work on Popperian problems has frequently led me into conflict with Popper's own solutions.

In the present note I shall sketch my position on what Popper himself frequently referred to as the two main problems of his now classical Logik der Forschung: the problem of demarcation and the problem of induction. Popper first gave a solution of the problem of demarcation and then, having claimed that ‘the problem of induction is only an instance or facet of the problem of demarcation’, he applied his demarcation criterion to solve the problem of induction. In my view, Popper's solution of the problem of demarcation is a great achievement but can be improved upon, and even in its improved form opens up large problems hitherto unsolved.