This is arguably the seminal work in historical and philosophical analysis of the twentieth century. Originally delivered for the William James lecture series at Harvard University in 1932-33, it remains the cornerstone of the history of ideas. Lovejoy sees philosophy's history as one of confusion of ideas, a prime example of which is the idea of a "great chain of being"--a universe linked in theology, science and values by pre-determined stages in all phases of life. Lovejoy's view is one of dualities in nature and society, with both error and truth as part of the natural order of things. The past reminds us that the ruling modes of thought of our own age, which we may view as clear, coherent and firmly grounded, are unlikely to be seen with such certainty by posterity. The Great Chain of Being is an excursion into the past, with a clear mission--to discourage the assumption that all is known, or that what is known is not subject to modifi cation at a later time. Lovejoy reaffirms the "intrinsic worth of diversity," as a caution against certitude. By this he does not mean toleration of indiff erence, or relativity for its own sake, but an appreciation of mental and physical process of human beings. As Peter Stanlis notes in his introduction: "Faith in the great chain of being was fi nally largely extinguished by the combined infl uences of Romantic idealism, Darwin's theory of evolution, and Einstein's theory of relativity." Few books remain as alive to prospects for the future by reconsidering follies of the past as does Lovejoy's stunning work.