Georges Dicker here provides a commentary on John Locke's masterwork, An Essay Concerning Human Understanding-the foundational work of classical Empiricism. Dicker's commentary is an accessible guide for students who are reading Locke for the first time; a useful research tool for upper-level undergraduate and graduate students; and a contribution to Locke scholarship for professional scholars. It is designed to be read alongside the Essay, but does not presuppose familiarity with it. Dicker expounds and critically discusses the main theses and arguments of each of the Essay's four books, on the innatism that Locke opposes, the origin and classification of ideas, language and meaning, and knowledge, respectively. He analyses Locke's influential explorations of related topics, including primary and secondary qualities, substance, identity, personal identity, free will, nominal and real essences, perception, and external-world skepticism, among others. Written in an analytical style that strives for clarity, the book offers careful textual analyses as well as step-by-step reconstructions of Locke's arguments, and it references and engages with relevant work of other major philosophers and Locke commentators.