John Locke's complex masterpiece, An Essay of Human Understanding, was a sustained attack on the dogmatism of the day and the last great work of philosophical realism before the onset of idealism. One of the most influential books in the history of thought, it is the most renowned work of the great English philosopher. Originally published in two volumes, this one-volume edition of Locke examines the historical meaning and philosophical significance of this work through careful explanations of the context of debate to which it was a decisive contribution. The first volume of this comprehensive work focuses on Locke's Essay from the epistemological side, and the second turns to the concepts of Locke's ontology--substance, mode, essence, law, and identity.