Is microphysics incomplete?

By microphysics we mean, roughly speaking, the physics of elementary particles and their interactions. The question we ask is whether knowledge of microphysics suffices, in principle, to determine the physics and chemistry of larger assemblages of inert matter. Since there seems to be little more than expressions of opinion on this subject, we infer that the question is regarded as belonging more to metaphysics than to physics. In this paper we attempt to analyse it in such a way as to arrive at precisely defined mathematical problems, the solution of which may allow one to give a non-metaphysical answer to the question. The paper is organized as follows. The Introduction describes how we arrived at the problem. It is followed by a section on Philosophical Considerations, in which we explain (mainly in the words of Bertrand Russell) the atomic theory of the ancient Greeks, to understand what should be kept and what should be set aside. Next comes one on The Structure of Physical Theories, in which we develop the notions of reduced descriptions, observational windows and relative atomism, which are our main analytical tools. They allow us to reduce the problem to mathematical ones in the next section, entitled States of Matter in Nonrelativistic Physics. They also allow us to say a bit more, which is done in the sections on Reversibility and the Arrow of Time, Remarks (in which biological systems are touched upon), and a Summing-up.