This book originally appeared in Japanese in 1973 in the Iwanami Series of Fundamental Physics supervised by Professor Hideki Yukawa and pub lished by Iwanami-Shoten. A revised second edition was published in 1978. The task we set ourselves was to grasp the properties of matter as a whole in a unified scheme and to present a general view of matter incor porating the results of modern physics. To achieve this goal we have tried to explore the laws which describe the structure of macroscopic matter, namely, to ask in what kinds of phy sical states matter can, in principle, exist and why. Thus,...