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.