John Locke (1632-1704) was educated at Christ Church, Oxford and held various academic posts at that university, lecturing on Greek and rhetoric. However, his interests lay in medicine and the new experimental sciences and in 1667 he became personal physician to the Earl of Shaftesbury. Under the influence of Shaftesbury, Locke developed his ideas on politics, property, trade, monarchy and the mind. Shaftesbury became a bitter opponent of Charles II and was involved in the plot of 1683. This forced Locke to flee in exile to Holland, but he returned after 1688 and began to publish his most famous works. He wrote also on ethology, education, and in defense of religious tolerance, while founding the analytic philosophy of the mind.

Introduction
Further Reading
Bibliographical Abbreviations
A Note on the Text
Title-page of the Fifth Edition
AN ESSAY CONCERNING HUMAN UNDERSTANDING
The Epistle Dedicatory
The Epistle to the Reader
The Contents
Book I: Of Innate Notions
I Introduction
II No Innate Principles in the Mind
III No Innate Practical Principles
IV Other Considerations concerning Innate Principles, both Speculative and Practical
Book II: Of Innate Notions
I Of Ideas in General, and their Original
II Of Simple Ideas
III Of Ideas of One Sense
IV Of Solidity
V Of Simple Ideas of Divers Senses
VI Of Simple Ideas of Reflection
VII Of Simple Ideas of both Sensation and Reflection
VIII Some further Considerations concerning our Simple Ideas
IX Of Perception
X Of Retention
XI Of Discerning, and other Operations of the Mind
XII Of Complex Ideas
XIII Of Simple Modes; and first, of the Simple Modes of Space
XIV Of Duration, and its Simple Modes
XV Of Duration and Expansion, considered together
XVI Of Number
XVII Of Infinity
XVIII Of other Simple Modes
XIX Of the Modes of Thinking
XX Of Modes of Pleasure and Pain
XXI Of Power
XXII Of Mixed Modes
XXIII Of our Complex Ideas of Substances
XXIV Of Collective Ideas of Substances
XXV Of Relation
XXVI Of Cause and Effect, and other Relations
XXVII Of Identity and Diversity
XXVIII Of other Relations
XXIX Of Clear and Obscure, Distinct and Confused Ideas
XXX Of Real and Fantastical Ideas
XXXI Of Adequate and Inadequate Ideas
XXXII Of True and False Ideas
XXXIII Of the Association of Ideas
Book III: Of Words
I Of Words or Language in General
II Of the Signification of Words
III Of General Terms
IV Of the Names of Simple Ideas
V Of the Names of Mixed Modes and Relations
VI Of the Names of Substances
VII Of Particles
VIII Of Abstract and Concrete Terms
IX Of the Imperfection of Words
X Of the Abuse of Words
XI Of the Remedies of the Foregoing Imperfections and Abuses
Book IV: Of Knowledge and Opinion
I Of Knowledge in General
II Of the Degrees of Our Knowledge
III Of the Extent of Human Knowledge
IV Of the Reality of Knowledge
V Of Truth in General
VI Of Universal Propositions, their Truth and Certainty
VII Of Maxims
VIII Of Trifling Propositions
IX Of our Knowledge of Existence
X Of our Knowledge of the Existence of a God
XI Of our Knowledge of the Existence of Things
XII Of the Improvement of our Knowledge
XIII Some further Considerations concerning our Knowledge
XIV Of Judgment
Xv Of Probability
XVI Of the Degrees of Assent
XVII Of Reason
XVIII Of Faith and Reason, and their Distinct Provinces
XIX Of Enthusiasm
XX Of Wrong Assent, or Error
XXI Of the Division of the Sciences

Appendix:
John Locke's Debate with Edward Stillingfleet, Bishop of Worcester, as it figures in footnotes in the Fifth Edition of the Essay
Index to the Fifth Edition
Notes