The empirical successes of atomic, nuclear, and particle physics have not reduced -- and may never fully resolve -- the philosophical controversies about the inner constitution of matter. This book examines these debates by exploring the particle concept in physics. Are the particles of modern physics "real" or are they fictitious entities, their existence deduced merely by the careless application of abstract theories? Or are the philosophers involved in the debate about "scientific realism" dedicating themselves to a problem that has long been solved by physicists? Studies of the experimental basis and theoretical relevance of the particle concept reveal that these questions are far from easy to answer, because, since the introduction of quantum theory, physical science no longer possesses a single unambiguous particle concept. All those interested in the "true meaning" of such physical concepts will find this book informative and thought provoking. It is written at a level accessible to scholars, students and teachers of science and philosophy.

Zusammenfassung
Metaphysics, with which, as fate would have it, I have fallen in love but from which I can boast of only a few favours, o?ers two kinds of advantage. The ?rst is this: it can solve the problems thrown up by the enquiry of mind, when it uses reason to spy after the more hidden properties of things. But hope is here all too often disappointed by the outcome. And, on this occasion, too, satisfaction has escaped our eager grasp. [...] The second advantage of metaphysics is more consonant with the nature of the human understanding. It consists [...] in knowing what relation the question has to empirical concepts, upon which all our judgements must at all times be based. To that extent metaphysics is a science of the limits of human reason.[...] Thus, the second advantage of metaphysics is at once the least known and the most important, although it is also an advantage which is only attained at a fairly late stage and after long experience. 1 Immanuel Kant The tradition of the particle concept goes back to traditional metaphysics and ancient philosophy. The idea that matter is made up of microscopic constituent parts stems from ancient atomism. At the very beginnings of modern physics, it was taken up by Galileo, Descartes, and Newton. Newton thought that there are atoms of matter and light, but with the methods of Newtonian mechanics and optics they were beyond the reach of experiments.

Inhalt
Scientific Realism.- Extending Physical Reality.- Particle Observation and Measurement.- Probing Subatomic Structure.- Measurement and the Unity of Physics.- Metamorphoses of the Particle Concept.- Wave-Particle Duality.- Subatomic Reality.