 Laudan's most influential book is "Progress and Its Problems" (1977), in which he charges philosophers of science with paying lip service to the view that "science is fundamentally a problem-solving activity" without taking seriously the view's implications for the history of science and its philosophy, and without questioning certain issues in the historiography and methodology of science.Against empiricism, which is represented by Karl Popper, and "revolutionism," represented by Thomas Kuhn, Laudan maintained in "Progress and Its Problems" that science is an evolving process that accumulates more empirically validated evidence while solving conceptual anomalies at the same time.Mere evidence collecting or empirical confirmation does not constitute the true mechanism of scientific advancement; conceptual resolution and comparison of the solutions of anomalies provided by various theories form an indispensable part of the evolution of science.