What is the nature of scientific progress and what makes it possible? When we look back at the scientific theories of the past and compare them to the state of science today, there seems little doubt that we have made progress. But how have we made this progress? Is it a continuous process which gradually incorporates past successes into present theories, or are entrenched theories overthrown by superior competitors in a revolutionary manner? Theories of Scientific Progress presents the arguments for and against both these extremes, and the positions in between. It covers the interpretations of scientific progress from William Whewell through Karl Popper and Imre Lakatos to Thomas Kuhn and beyond, to the latest contemporary debates. Along the way John Losee introduces and discusses questions about evidential support and the comparison of theories; whether scientific progress aims at truth or merely problem-solving effectiveness; what mechanisms underlie either process; and whether there are necessary or sufficient conditions for scientific progress. He ends with a look at the analogy between the growth of science and the operation of natural selection in the organic world, and the current ideas of evolutionary theorists such as Stephen Toulmin and Michael Ruse. Theories of Scientific Progress is the ideal introduction to this topic. It is clearly organised, with suggestions for further reading which point the way to both primary texts and secondary literature. It will be essential reading for students of the history and philosophy of science.