 In the early twentieth century, analytic philosophers of science started to apply modern logic to the study of science. Their main focus was the structure of scientific theories and patterns of inference (Suppe 1977). This “synchronic” investigation of the “finished products” of scientific activities was questioned by philosophers who wished to pay serious attention to the “diachronic” study of scientific change. Among these contributions one can mention N.R. Hanson’s Patterns of Discovery (1958), Karl Popper’s The Logic of Scientific Discovery (1959) and Conjectures and Refutations (1963), Thomas Kuhn’s The Structure of Scientific Revolutions (1962), Paul Feyerabend’s incommensurability thesis (Feyerabend 1962), Imre Lakatos’ methodology of scientific research programmes (Lakatos and Musgrave 1970), and Larry Laudan’s Progress and Its Problems (1977). Darwinist models of evolutionary epistemology were advocated by Popper’s Objective Knowledge: An Evolutionary Approach (1972) and Stephen Toulmin’s Human Understanding (1972). These works challenged the received view about the development of scientific knowledge and rationality. Popper’s falsificationism, Kuhn’s account of scientific revolutions, and Feyerabend’s thesis of meaning variance shared the view that science does not grow simply by accumulating new established truths upon old ones. Except perhaps during periods of Kuhnian normal science, theory change is not cumulative or continuous: the earlier results of science will be rejected, replaced, and reinterpreted by new theories and conceptual frameworks. Popper and Kuhn differed, however, in their definitions of progress: the former appealed to the idea that successive theories may approach towards the truth, while the latter characterized progress in terms of the problem-solving capacity of theories. 