2017 June John Locke

John Locke, An Essay Concerning Human Understanding (1689)


John Locke, An Essay Concerning Human Understanding (London, 1700), front piece portrait


What is the source of our knowledge? What are the limits of human understanding?

These are amongst the most important questions that John Locke sought to investigate when in 1689 he published, An Essay Concerning Human Understanding.

John Locke was born in England in 1632, the son of a legal clerk who later participated in the English Civil War (1642–1651), supporting the Parliamentarians. He was educated at both Westminster College and the University of Oxford. Having secured a number of posts at Oxford he left the university in 1667 to take up a role within the household of Anthony Ashley Cooper, later the Earl of Shaftesbury (1621-1683). From 1675 he travelled to both France and the Netherlands. He returned to England in the aftermath of the Glorious Revolution of 1688 and in 1689 published his magnum opus. This Book of the Month will touch upon a number of significant ideas in the work but brevity will not allow full justice to be given to the scope of Locke’s ambitious project.

The work is divided into four books.

Book I examines the possibility that as humans we have access to innate knowledge.

Book II advances Locke’s arguments that experience is the source of human ideas.

Book II explores the role that language plays in our understanding of knowledge.

Book IV examines what constitutes knowledge and whether there are limits to our knowledge.


John Locke, An Essay Concerning Human Understanding (London, 1700), title page


Locke begins his investigation in Book I by interrogating the source of our ideas which are the basis on which we construct knowledge. He challenges the prominent contemporary idea that humans possessed innate ideas. He does this by subjecting innateness to empirical analysis and concludes that there is no strong evidence to support it. Innate ideas are those which are ‘stamped upon the Mind of Man, which the Soul receives in its very first Being; and brings into the world with it’ (I.2.1.). Locke challenges some of the arguments advanced in favour of innate ideas. For example, the argument of universal consent argues that there are principles which are universally agreed upon by all humans which are held to support the existence of innate ideas. For Locke, not only does universal agreement not equate to innateness, but he denies the existence of universal agreement. He uses the example of children and the mentally disabled not comprehending certain propositions to disprove the existence of universal assent:

‘If therefore children and Idiots have souls, have minds, with those Impressions upon them, they must unavoidably perceive them, and necessarily know and assent to these Truths, which, since they do not, it is evident that there are no such Impressions. For if they are not Notions naturally imprinted, How can they be innate? And if they are Notions imprinted, How can they be unknown? To say a Notion is imprinted on the Mind, and yet at the same time to say, that the mind is ignorant of it, and never yet took notice of it, is to make this Impression nothing’. (I.2.5.)


This challenge to innate ideas was not simply epistemological but had far reaching practical implications, especially with regard to the basis for belief in a wide variety of issues. This was appreciated by Locke who wrote that belief in innate ideas ‘eased the lazy from the pains of search, and stopp’d the inquiry of the doubtful concerning all that was once styled innate: and it was of no small advantage to those who affected to be Masters and Teachers, to make this the Principle of Principles, That principles must not be questioned’. Such a position ensured that individual reason and judgement were not considered adequate. The result was a ‘posture of blind Credulity’ so that people could ‘be more easily governed by, and made useful to, some sort of Men, who had the skill and office to principle and guide them’. This has significant consequences for human relations as it gives certain individuals the power ‘to have the Authority to be the Dictator of Principles, and Teacher of unquestionable Truths’ (I.4.24.).


John Locke, An Essay Concerning Human Understanding (London, 1700), II.11.17


Book II is concerned with Locke’s explanation of the source of ideas and knowledge. Locke maintains that experience is the source of all knowledge. He wrote that prior to experience the mind is ‘white Paper, void of all Characters, without any Ideas’, what later writers would refer to as a tabula rasa (blank slate). He advances two types of experience: ‘Our Observation employ’d either about external Sensible Objects; or about the internal Operations of our Minds, perceived and reflected on by our selves, is that, which Supplies our Understandings with all the materials of thinking’ (II.1.2.) The former are the ideas that are provided from our five senses. The latter refers to the mind reflecting upon its own operations, examples include thinking, believing, remembering, doubting. These two experiences provide us with simple ideas, the basic and fundamental units of thought, examples include colours and sounds. For Locke our minds can put a variety of simple ideas together to form complex ideas which can be of different varieties: ideas of modes, substances, and relations. Ideas of relations are relational concepts (eg. brother). Substances have independent existences (eg. animals). Modes are dependent upon substances (eg. numbers). These lead Locke to a discussion of a wide variety of ideas such as space, time, and solidity amongst other topics, as well as his exposition of the primary and secondary qualities of objects. Primary qualities are the characteristics of objects that exist independently of a perceiver such as its shape, texture, solidity, etc. whilst secondary qualities are the ability to produce ideas in perceivers such as colours, taste, smell, etc. This distinction is central to Locke’s examination of language in Book III.


John Locke, An Essay Concerning Human Understanding (London, 1700), Book IV.19.1


This book is mainly focused upon the relationship between ideas and words. He investigates the names of substances and modes and argues that physical substance is composed of atoms about which we have no experience. We are familiar with the primary and secondary qualities (nominal essence) but have no knowledge of the composition at an atomic level (real essence). As a result our naming conventions do not derive from the real essence. Here, Locke aims to highlight how the misuse of language is a barrier to knowledge. Language is the primary means of communication between humans and how we express our ideas. But, we also need our words to convey the same idea to those with whom we are communicating or else communication through language would be impossible. Some problems that arise include that words do not carry constant meanings. The meaning of the words used may also not be the same as the nature of that which it denotes. Many of our words convey complex ideas which some will experience difficulty in using in the suitable way due to an insufficient understanding of its meaning. The solutions Locke proposes are only using words of which we have a clear idea and ones that consistently represent the same idea, as well as defining words where necessary.


John Locke, An Essay Concerning Human Understanding (London, 1700), Book IV.16.4


Book IV is concerned with what constitutes knowledge and the limits of human understanding. Knowledge is defined as ‘the perception of the connexion and agreement, or disagreement and repugnancy of any of our Ideas’ (IV.1.2.). If knowledge is only possible through perception humans are limited in what they can know with certainty. If the real essence is unavailable to us our knowledge of the material world relies on probability rather than certainty. Locke primarily focuses on two main types of knowledge. Intuitive knowledge when the individual directly perceives the relationship between ideas. Demonstrative knowledge is the perception of the relationship between ideas through intermediate ideas. The work confines the extent of human knowledge within a limited scope. Locke encouraged his readers not to despair at his conclusions arguing that ‘some Things are not to be understood’ and we have sufficient knowledge for our needs. He wrote that,

‘Tis of great use to the Sailor, to know the length of his Line, though he cannot with it fathom all the depths of the Ocean. ‘Tis well he knows, that it is long enough to reach the bottom, at such Places, as are necessary to direct his Voyage, and caution him against running upon Shoals, that may ruin him. Our Business here is not to know all things, but those which concern our Conduct. If we can find out those Measures, whereby a rational Creature put in that State, in which Man is in, in this World, may, and ought to govern his Opinions, and Actions depending thereon, we need not to be troubled that some other things escape our Knowledge (I.1.6.).

Edward Worth’s collection includes not only a copy of An Essay Concerning Human Understanding but also Locke’s later work Two Treatises on Government (1689), a landmark publication in political philosophy that was to exert an influence on both the American and French Revolutions. The collection also includes the collected works of John Locke which contain other influential texts including, A Letter Concerning Toleration (1689), Some Thoughts concerning Education (1693), and The Reasonableness of Christianity (1695).

The influence of Locke’s work was immense and his empiricist epistemology was to have a seminal influence upon the growth of the Enlightenment. Hans Aarsleff has called Locke ‘the most influential philosopher of modern times’ on the basis that his work ‘set us free from the burden of tradition and authority, both in theology and knowledge, by showing that the entire grounds of our right conduct in the world can be secured by the experience we may gain by the innate faculties and powers we are born with’. Locke’s work also played a central role in the development of views on religious toleration and was an important influence on the the work of later writers such as John Toland (1670-1722), Anthony Collins (1676-1729), and Matthew Tindal (1657-1733). This influence is explored in our exhibition ‘Deism and the Early Enlightenment at the Edward Worth Library‘.



Aarsleff, Hans, ‘Locke’s Influence’ in, Vere Chappell (ed.), The Cambridge Companion of Locke (Cambridge, 1994), pp. 252-289.

Connolly, Patrick J., ‘John Locke (1632—1704)’, The Internet Encyclopedia of Philosophy, URL = http://www.iep.utm.edu/locke/. [Accessed 07/03/17].

Lowe, Edward Jonathan, Locke (New York, 2005).

Newman, Lex, (ed.), The Cambridge Companion to Locke’s Essay Concerning Human Understanding (Cambridge, 2007).

Pyle, A.J., Locke (London, 2013).

Rickless, Samuel, Locke (Malden, 2014).

Uzgalis, William, ‘John Locke’, The Stanford Encyclopedia of Philosophy (Spring 2016 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2016/entries/locke/>. [Accessed 07/03/17].


Text by Dr Brendan Power, Edward Worth Library


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