Physician-scientist Lewis Thomas turns to pressing, threatening issues in this collection of 24 essays, many of which have been published in Discover magazine. The book opens and closes with meditations on nuclear warfare--the atom bombs of World War II and the escalation of worldwide tensions and technology that can combine to destroy the human race. In between, other essays, such as "On Medicine and the Bomb" and "Science and 'Science,'" also focus on these issues.

Less apocalyptic essays concern Thomas's experience with requiring a pacemaker, the state of psychiatry, lie detectors as evidence for essential human morality, and his abiding interest in language and scientific research.