This book describes the framework of a new theory of science. Over the last hundred years, philosophy of science has developed its theory based on what philosophers perceived what science is and what scientists do. It does not address the basic questions that scientists care about. Thus, this book examines the conventional theories of philosophy of science from a completely different point of view and describes the most difficult problems that scientists are concerned about and how science is conducted. This book is based on the lecture notes under the same title in Honors College at the junior level in UMASS Lowell. It is qualified as a required course in Art and Humanity for science and engineering majors.