Science in Context 18(3), 479–509 (2005). Copyright C  Cambridge University Press doi:10.1017/S0269889705000621 Printed in the United Kingdom The Science of Complexity: Epistemological Problems and Perspectives Giorgio Israel Universit` a di Roma “La Sapienza” Argument For several decades now a set of researches from a wide range of different sectors has been developed which goes by the name of “science of complexity” and is opposed point by point to the paradigm of classical science. It challenges the idea that world is “simple.” To the reductionist idea that each process is the sum of the actions of its components it opposes a holistic view (the whole is more than the sum of the parts). The aim of the present article is to analyze the epistemological status attributed in the science of complexity to several fundamental ideas, such as those of scientific law, objectivity, and prediction. The aim is to show that the hope of superseding reductionism by means of concepts such as that of “emergence” is fallacious and that the science of complexity proposes forms of reductionism that are even more restrictive than the classical ones, particularly when it claims to unify in a single treatment problems that vary widely in nature such as physical, biological, and social problems. 1. Introduction: on the notion of complexity Scientific terms may be roughly divided into two categories: those that are introduced by means of a precise and even formal definition (which is the case for many of the more recent mathematical terms) and those that are drawn from everyday language and which have further to travel before they attain the status of an unequivocal definition. The word “complexity” (from the Latin complecti, grasp, comprehend, embrace) belongs to the second category and is particularly resistant to precise definition. This is also because it is often confused with the word “complication” (from the Latin complicare, fold, envelop), and because both terms are mostly used to mean the opposite of “simple.” 1 This negative characterization is undeniably effective despite its vagueness, as it captures one of the central aspects of the role played by the concept of complexity in contemporary science: this consists of the radical opposition to a central idea of classical science, namely that the structure of the world is fundamentally simple and that the essence of scientific analysis lies in resolving (dissolving) the apparent complexity of 1 On these topics see the excellent overview contained in Lepschy 2004a; see also Lepschy 2004b and Lepschy 2000.