This volume is a logical sequel of Volume I, The Search for System: indeed, it concerns the ways theoretical systems are put to work and subjected to test. Yet it can be read independently by anyone familiar with some factual theories, referring back to Volume I when necessary. Special Symbols AS;B the set A is included in the set B AvB the union of the sets A and B AnB the common part of the sets A and B aEB the individual a is in (or belongs to) the set A Card (A) cardinality (numerosity) of the set A AxB Cartesian product of the sets A and B en(A) consequence(s) of the set A of assumptions equals by definition =dt definition Dt· some x (or there is at least one x such that) (3 x) e empirical datum e* translation of e into a semiempirical, semitheoreticallanguage h hypothesis m(r) measured value of the degree r m(;) average (or mean) value of a set of measured values of ,; P-jT T presupposes P p, q arbitrary (unspecified) propositions (statements) P(x) x has the property P (or x is a P) {xl P(x)} set of the x such that every x is a P pVq p and/or q (inclusive disjunction) p &q p and q (conjunction) p-+q if p, then q (conditional or implication) p if and only if q (biconditional or equivalence) p-q sum over i 2:; t theorem, testable consequence

This is a collection of technical papers in the foundations and the philoso­ It takes both "foundations" phy of physics with emphasis on the former. and "philosophy" in their narrow technical senses but it construes "physics" lato sensu, as including all the sciences of nonliving systems. All eleven papers constituting this volume were written for it. The problems tackled in this book concern certain basic concepts, hypotheses, theories, and research programmes in physical science. Some of these problems are topical, others new, but they are all fundamental and the subject of research and controversy. Consequently this volume is expected to serve those students, teachers and researchers who enjoy learning, teaching, discussing or doing theoretical physics. It is addressed to the nine to niners rather than to the nine to fivers. It is expected to attract the theoretician in search for new basic ideas, the teacher eager to perfect his understanding of physical theory and transmit his own zeal and his own doubts, as well as the student anxious to get down to essentials. This book may also interest the mathematician for whom physics offers a challenge (or a good pretext). Finally, it should get the attention of the philosopher of science aware of the advantages of philosophizing on foundations research problems rather than on the popularization of some results of research. There are at least two reasons for valuing foundations research.

This volume collects the lectures on the foundations of physics given by eleven scientists at the University of Delaware. It is neither an anthology of disconnected items nor a smoothly running textbook but rather a progress report on a neglected yet vital area of basic physical research, namely foundations research. The investigation into the foundations of any branch of science is neither loose speculation nor popular science: it is an aspect of scientific research - in fact the deepest-searching part of basic research. Con­ sequently it must be carried out by the scientist himself. Thus whether the time concept is a numerical variable or a function, whether particle mechanics is the primary mechanical theory or a particular case of continuum mechanics, whether transformation formulas are laws of nature or links between equivalent descriptions, whether thermodynamics has been fully reduced to statistical mechanics, whether the field concept is dispensable, whether the covariance principle is a law or a regulative principle, whether quantum mechanics is completely detached from classical physics or contains fragments of it, whether it has annihilated the physical object or given a more complex picture of it, and to which extent are the field variables measurable - all these are technical questions demanding a careful analysis of pieces of recent basic research. Yet all of these problems and indeed all questions in foundational research are philosophical as well as scientific.

This volume is a logical sequel of Volume I, The Search for System: indeed, it concerns the ways theoretical systems are put to work and subjected to test. Yet it can be read independently by anyone familiar with some factual theories, referring back to Volume I when necessary. Special Symbols AS;B the set A is included in the set B AvB the union of the sets A and B AnB the common part of the sets A and B aEB the individual a is in (or belongs to) the set A Card (A) cardinality (numerosity) of the set A AxB Cartesian product of the sets A and B en(A) consequence(s) of the set A of assumptions equals by definition =dt definition Dt· some x (or there is at least one x such that) (3 x) e empirical datum e* translation of e into a semiempirical, semitheoreticallanguage h hypothesis m(r) measured value of the degree r m(;) average (or mean) value of a set of measured values of ,; P-jT T presupposes P p, q arbitrary (unspecified) propositions (statements) P(x) x has the property P (or x is a P) {xl P(x)} set of the x such that every x is a P pVq p and/or q (inclusive disjunction) p &q p and q (conjunction) p-+q if p, then q (conditional or implication) p if and only if q (biconditional or equivalence) p-q sum over i 2:; t theorem, testable consequence

This is a collection of technical papers in the foundations and the philoso­ It takes both "foundations" phy of physics with emphasis on the former. and "philosophy" in their narrow technical senses but it construes "physics" lato sensu, as including all the sciences of nonliving systems. All eleven papers constituting this volume were written for it. The problems tackled in this book concern certain basic concepts, hypotheses, theories, and research programmes in physical science. Some of these problems are topical, others new, but they are all fundamental and the subject of research and controversy. Consequently this volume is expected to serve those students, teachers and researchers who enjoy learning, teaching, discussing or doing theoretical physics. It is addressed to the nine to niners rather than to the nine to fivers. It is expected to attract the theoretician in search for new basic ideas, the teacher eager to perfect his understanding of physical theory and transmit his own zeal and his own doubts, as well as the student anxious to get down to essentials. This book may also interest the mathematician for whom physics offers a challenge (or a good pretext). Finally, it should get the attention of the philosopher of science aware of the advantages of philosophizing on foundations research problems rather than on the popularization of some results of research. There are at least two reasons for valuing foundations research.

This volume collects the lectures on the foundations of physics given by eleven scientists at the University of Delaware. It is neither an anthology of disconnected items nor a smoothly running textbook but rather a progress report on a neglected yet vital area of basic physical research, namely foundations research. The investigation into the foundations of any branch of science is neither loose speculation nor popular science: it is an aspect of scientific research - in fact the deepest-searching part of basic research. Con­ sequently it must be carried out by the scientist himself. Thus whether the time concept is a numerical variable or a function, whether particle mechanics is the primary mechanical theory or a particular case of continuum mechanics, whether transformation formulas are laws of nature or links between equivalent descriptions, whether thermodynamics has been fully reduced to statistical mechanics, whether the field concept is dispensable, whether the covariance principle is a law or a regulative principle, whether quantum mechanics is completely detached from classical physics or contains fragments of it, whether it has annihilated the physical object or given a more complex picture of it, and to which extent are the field variables measurable - all these are technical questions demanding a careful analysis of pieces of recent basic research. Yet all of these problems and indeed all questions in foundational research are philosophical as well as scientific.