ABSTRACT
Herman Feshbach, the organizer of this symposium in honor of Niels Bohr, asked the author in his original invitation, for a review of the present state of condensed matter physics, with emphasis on major unsolved problems and comments on any overlap with Bohr's ideas regarding the fundamentals of quantum mechanics. Condensed matter physics is a multifaceted subject-a beautiful diamond. The aim of this chapter is to hold this diamond up to view and to turn it around, alas rather rapidly, so that a few flashes may catch the eye. The chapter discusses several interesting forms of matter, describing in each case the experimental situation and then giving some idea of our theoretical understanding and concurrently pointing out the degree to which quantum mechanics enters. Polymers are long molecules with some finite thickness: the importance of their thickness has been stressed by many researchers, most notably P. J. Flory, and is realized to be a crucial feature determining their behavior.
