Imre Lakatos' thought is very fascinating, but it is also fascinating to study the development of his thought. This development is not at all linear and uniform. On the contrary it is full of great upheavals, and dramatic changes of direction. The works of philosophers who often change their opinion, usually give the impression of a lack of any coherent position. Strange to say, the works of Lakatos, despite his frequent changes of opinion, do not give this impression. The reason for this paradoxical situation is perhaps that at the centre of Imre Lakatos' philosophy there is a dialectical concept of continual change. His own changes of opinion are, consequently, compatible with his philosophical vision of the world.