In this sequence of philosophical essays about natural science, Nancy Cartwright argues that fundamental explanatory laws, the deepest and most admired successes of modern physics, do not in fact describe the regularities that exist in nature. Yet she is not `anti-realist'. Rather, she draws a novel distinction, arguing that theoretical entities, and the complex and localized laws that describe them, can be interpreted realistically, but that the simple unifying laws of basic theory cannot.

How fixed are the happenings in Nature and how are they fixed? These lectures address what our scientific successes at predicting and manipulating the world around us suggest in answer. One—very orthodox—account teaches that the sciences offer general truths that we combine with local facts to derive our expectations about what will happen, either naturally or when we build a device to design, be it a laser, a washing machine, an anti-malarial bed net, or an auction for the airwaves. In these three 2017 Carus Lectures Nancy Cartwright offers a different picture, one in which neither we, nor Nature, have such nice rules to go by. Getting real predictions about real happenings is an engineering enterprise that makes clever use of a great variety of different kinds of knowledge, with few real derivations in sight anywhere. It takes artful modeling. Orthodoxy would have it that how we do it is not reflective of how Nature does it. It is, rather, a consequence of human epistemic limitations. That, Cartwright argues, is to put our reasoning just back to front. We should read our image of what Nature is like from the way our sciences work when they work best in getting us around in it, non plump for a pre-set image of how Nature must work to derive what an ideal science, freed of human failings, would be like. Putting the order of inference right way around implies that like us, Nature too is an artful modeler. Lecture 1 is an exercise in description. It is a study of the practices of science when the sciences intersect with the world and, then, of what that world is most likely like given the successes of these practices. Millikan's famous oil drop experiment, and the range of knowledge pieced together to make it work, are used to illustrate that events in the world do not occur in patterns that can be properly described in so-called "laws of nature." Nevertheless, they yield to artful modeling. Without a huge leap of faith, that, it seems, is the most we can assume about the happenings in Nature. Lecture 2 is an exercise in metaphysics. How could the arrangements of happenings come to be that way? In answer, Cartwright urges an ontology in which powers act together in different ways depending on the arrangements they find themselves in to produce what happens. It is a metaphysics in which possibilia are real because powers and arrangement are permissive—they constrain but often do not dictate outcomes (as we see in contemporary quantum theory). Lecture 3, based on Cartwright's work on evidence-based policy and randomized controlled trials, is an exercise in the philosophy of social technology: How we can put our knowledge of powers and our skills at artful modeling to work to build more decent societies and how we can use our knowledge and skills to evaluate when our attempts are working. The lectures are important because: They offer an original view on the age-old question of scientific realism in which our knowledge is genuine, yet our scientific principles are neither true nor false but are, rather, templates for building good models. Powers are center-stage in metaphysics right now. Back-reading them from the successes of scientific practice, as Lecture 2 does, provides a new perspective on what they are and how they function. There is a loud call nowadays to make philosophy relevant to "real life." That's just what happens in Lecture 3, where Cartwright applies the lesson of Lectures 1 and 2 to argue for a serious rethink of the way that we are urged—and in some places mandated—to use evidence to predict the outcomes of our social policies.

This book presents a radical new picture of natural order. The Newtonian idea of a cosmos ruled by universal and exceptionless laws has been superseded; replaced by a conception of nature as a realm of diverse powers, potencies, and dispositions, a 'dappled world'. There is order in nature, but it is more local, diverse, piecemeal, open, and emergent than Newton imagined. In each chapter expert authors expound the historical context of the idea of laws of nature, and explore the diverse sorts of order actually presupposed by work in physics, biology, and the social sciences. They consider how human freedom might be understood, and explore how Newton's idea of a 'universal designer' might be revised, in this new context. They argue that there is not one unified totalizing program of science, aiming at the completion of one closed causal system. We live in an ordered universe, but we need to rethink the classical idea of the 'laws of nature' in a more dynamic and creatively diverse way.

It is often supposed that the spectacular successes of our modern mathematical sciences support a lofty vision of a world completely ordered by one single elegant theory. In this book Nancy Cartwright argues to the contrary. When we draw our image of the world from the way modern science works - as empiricism teaches us we should - we end up with a world where some features are precisely ordered, others are given to rough regularity and still others behave in their own diverse ways. This patchwork makes sense when we realise that laws are very special productions of nature, requiring very special arrangements for their generation. Combining classic and newly written essays on physics and economics, The Dappled World carries important philosophical consequences and offers serious lessons for both the natural and the social sciences.

Originally published: Get a grip on new physics. London: Weidenfeld and Nicolson, 1999.

Natural and social sciences seem very often, though usually only implicitly, to hedge their laws by ceteris paribus clauses - a practice which is philosophically very hard to understand because such clauses seem to render the laws trivial and unfalsifiable. After early worries the issue is vigorously discussed in the philosophy of science and the philosophy of mind since ca. 15 years. This volume collects the most prominent philosophers of science in the field and presents a lively, controversial, but well-integrated, highly original and up-to-date discussion of the issue. It will be the reference book in the coming years concerning ceteris paribus laws.

This is the long awaited follow-up to Lie Algebras, Part I which covered a major part of the theory of Kac-Moody algebras, stressing primarily their mathematical structure. Part II deals mainly with the representations and applications of Lie Algebras and contains many cross references to Part I. The theoretical part largely deals with the representation theory of Lie algebras with a triangular decomposition, of which Kac-Moody algebras and the Virasoro algebra are prime examples. After setting up the general framework of highest weight representations, the book continues to treat topics as the Casimir operator and the Weyl-Kac character formula, which are specific for Kac-Moody algebras. The applications have a wide range. First, the book contains an exposition on the role of finite-dimensional semisimple Lie algebras and their representations in the standard and grand unified models of elementary particle physics. A second application is in the realm of soliton equations and their infinite-dimensional symmetry groups and algebras. The book concludes with a chapter on conformal field theory and the importance of the Virasoro and Kac-Moody algebras therein.