' ... there is an essential unity of theme and purpose running through all the papers collected in these volumes. Many of the papers, even though they have been previously published, are not fully self-contained and can be understood only by reference to others. Their collection and the editors' cross-referencing thus serves the useful purpose of facilitating an assessment of Lakatos' contribution to philosophy.' Philosophical Books ' ... a well-produced book that every philosopher of science or mathematics will wish to have.' Philosophy