This book is an extraordinary achievement by Jonathan Halevy. To condense the material of three major gastrointestinal textbooks would be triumph enough, but to add a distillate of the contents of ten journals, from 1980 to 1985, requires Herculean vigor. To reorganize all the material under headings which extract concise "facts" from wheat and chaff requires a passionate interest in pa­ tients together with an understanding of physiology. Fortunately, Jonathan Halevy has just the right combination of clinical and lab­ oratory interest for him to select the details of what is important. Such compulsive dedication has now made it possible for the prac­ ticing phYSician, gastroenterologist, or house officer, interested in preparing for board examinations or simply browsing in the field, to have at his fingertips a series of definitions and to put in his pocket the key facts for diagnosis and therapy. Of course, facts by themselves are something of which to be a little wary. Scientists first, doctors regard facts the way farmers look at sheep-to be sheared for their utility. Medicine too often is only a fact-gathering occupation (some lectures send me to wool­ gathering), in which having the facts sometimes clouds clinical judgment about what is important for the individual patient. - vii viii FOREWORD tionalism and romanticism lie at the two poles of medical practice, but rationalism rules in the 1980s.