John Locke: What are the Limits of Human Understanding?

John Locke was one of the foremost philosophers of the 17th century, whose work on the limits of understanding constitutes one of the most significant developments of modern philosophy

Dec 2, 2022By Luke Dunne, BA Philosophy & Theology

john locke on human understanding


John Locke is one of the most important philosophical figures of the 17th century. His work, uncommonly for philosophers today, fixed on a wide span of philosophical sub-disciplines, and he has proven enduringly influential in different ways for different kinds of philosopher. In politics, he offered one of the first substantial articulations of liberalism and remains a lodestar for liberal philosophers of all kinds today. He also offered a philosophical treatment of practical political issues – religious intolerance, war, slavery and so on. In metaphysics and mind, his engagement with questions of predisposition, nature, identity and will have all proven exceptionally influential. However, it is for his epistemology, specifically his formulation of the doctrine of empiricism and his articulation of the limits of human understanding, that he is best known.


The Origins of John Locke’s Philosophy: An Eventful Life 

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Godfrey Kellner’s portrait of John Locke, 1697, via the Hermitage Museum.


Even if it is somewhat nonsensical to describe one period of time as more eventful than another (according to who? according to what?), the period of English history through which John Locke lived was, in several important ways, extraordinarily hectic. Born in 1632, Locke’s early years were defined by the deterioration in the relationship between King Charles I and his Parliament, precipitating the exceptionally bloody English Civil War between the Puritan ‘Roundheads’ and the Royalist ‘Cavaliers’, in which Locke’s father fought for the former.


The period following King Charles’ defeat was, without a doubt, one of the most exciting and uncertain periods in English political history. The country undertook an 11 year experiment in republicanism, with Oliver Cromwell ruling as ‘Lord Protector’. No stable government was established in this time, and by the end of this period Locke had curated a number of influential friends, including Lord Ashley, who hired Locke as his personal physician in 1667 and thus gave him a front row seat to the various intrigues and controversies of English politics for the next two decades.


Political Upheaval and Intellectual Radicalism 

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Abraham van Blyenchurch’s portrait of Charles I, ca. 1616, via the National Portrait Gallery.


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This was a period of political radicalism, underpinned by exceptionally heated controversies surrounding religion – between Catholics and Anglicans, between Anglicans and non-conforming Protestants, between different Protestant denominations. Political upheaval was thoroughly intertwined with questions concerning the ultimate nature of reality. Religion wasn’t the only lens by which reality was to be examined.


John Locke’s generation of scholars and intellectuals included a number of exceptionally gifted scientists, mathematicians and philosophers, many of whom he was directly influenced by. The developments in philosophy, particularly those of Descartes, were certainly necessary for Locke’s philosophy to emerge in the way it did. In particular, the Cartesian notion of the ‘idea’, which are conceptions of the essence of things (such as mind, matter and God).


Master-builders and Under-labourers

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Samuel Cooper’s portrait of Oliver Cromwell, based on a work of 1656, via the National Portrait Gallery.


The developments in science were, if anything, even more significant. John Locke knew Robert Boyle well, and was familiar with his mechanical, empirically minded conception of reality before that of Descartes. The theory of ideas, to which philosophers after Descartes broadly subscribed, is that we have access to certain mental representations of the world called ideas, but not direct physical access to it. Although he was greatly influenced by Descartes’ theory of ideas, Locke was skeptical of the rationalism in Descartes, which indicated such ideas were innate.


It is very important to understand Locke’s philosophical work as concerned with making philosophical sense of the developments undertaken in the empirical sciences and mathematics. He observes at the outset of An Essay Concerning Human Understanding, his most important philosophical work, that “The commonwealth of learning is not at this time without master-builders, whose mighty designs, in advancing the sciences, will leave lasting monuments to the admiration of posterity”. His role, as he describes it, is as “an under-laborer in clearing the ground a little and removing some of the rubbish that lies in the way to knowledge”.


Locke’s Project: Investigating Human Understanding

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Johann Kerseboom’s portrait of Robert Boyle, ca. 1689-90, via the National Portrait Gallery.


It is difficult to say how genuine or ironic Locke’s self-deprecation is, but this conception of his role – if not its significance – seems to cohere with the project Locke undertakes in the Essay. But what, exactly, is that project? Roughly speaking, it concerns an attempt to investigate human understanding and its limits. One of the famous, early passages in the Essay serves to distinguish an investigation of the world from an investigation of human understanding and indicates that priority should be given to the latter.


Locke says that he “thought that the first Step towards satisfying the several Enquiries the Mind of Man was apt to run into, was, to take a Survey of our own Understandings, examine our own Powers, and see to what Things they were adapted. Till that was done, [he] suspected that we began at the wrong end.” That is, in direct contrast to treating the world and our enquiry into it, “as if all the boundless Extent, were the natural and undoubted Possessions of our Understandings, wherein there was nothing that escaped its Decisions, or that escaped its Comprehension.”


A Survey on the Limits of Understanding

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A bust of John Locke, via Wikimedia Commons.


Locke observed in his ‘Epistle to the Reader’, which functions as a kind of preface to the Essay, that the work which became the Essay arose originally out of conversations with friends. These intellectual debates – which we know involved such timely matters as the nature of God and the nature of Justice – were, on Locke’s account, going nowhere fast because they hadn’t paid sufficient attention to the conditions of knowledge. In other words, they had asked questions before asking what it would mean to understand the answers, or whether answers to such questions could be understood at all. It was the very basis of human understanding which Locke was to examine in detail, and it is worth emphasizing that this question was first put in terms of its limitations.


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Herman Verelst’s portrait of Locke, unknown date, via the National Portrait Gallery.


For Locke, inquiry begins by examining the world, by asking questions not about us, but about things external to (or at least separate to) ourselves. That is, our enquiries tend to begin, “as if all the boundless Extent, were the natural and undoubted Possessions of our Understandings, wherein there was nothing that escaped its Decisions, or that escaped its Comprehension”. Though this point isn’t made explicitly by Locke, that all of reality is naturally understood to fall within the range of human understanding seems to incline us towards an understanding of knowledge, or at least the capacity for knowledge, to be inscribed within us innately.


Are There Innate Ideas? What Are They?

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A marble bust of Aristotle, ca. 4th century BC, via Wikimedia Commons.


Certainly, the view that there are innate ideas prevailed both in the philosophy taught to Locke at Oxford, which was thoroughly medieval and therefore thoroughly Aristotelian, and in the modern, Cartesian philosophy which was becoming influential at that time. Locke begins his analysis of human understanding and its limitations by arguing that, contrary to prevailing philosophical and popular understandings of knowledge, the view that human knowledge is constituted by innate ideas is unfounded.


There are several definitions of an innate idea, and Locke spends time disputing the foundation of each. First, the conception of innate ideas as propositions imprinted in the mind, “some primary notions…Characters as it were stamped upon the Mind of Man, which the Soul receives in its very first Being; and brings into the world with it”. Here, an innate idea is, if not a precise sentence, then at the very least a semantic unit which each of us has within us pre-formed.


Locke Disagreed with His Contemporaries

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A photograph of Christ Church, Locke’s college at Oxford , via Wikimedia Commons.


Locke holds that even the most banal and uncontroversial candidates for the status of innate idea – such as, ‘What is, is’ – are not apparent to everyone. Whilst he suggests only children and idiots might fail to agree with ‘what is…is’, that is sufficient to demonstrate such ideas cannot be innate if that implies universality. Locke dismisses the notion that such ideas could be innate, but nonetheless unperceived or misunderstood by some, arguing “it seems to me a near Contradiction to say that there are truths imprinted on the Soul, which it perceives or understands not; imprinting if it signifies anything, being nothing else but the making certain Truths to be perceived.”


This problem is only exacerbated when moving from these theoretical principles to the realm of practical, moral principles. Though often taken to be innate, Locke observes the exceptional diversity of opinion as a significant mark against the view that moral principles are innate.


John Locke Against Innate Dispositions

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Illustration from Descartes’ “De Homine” published in 1662, via the Wellcome Collection.


Locke then turns to a different theory of innate ideas, which models them not as propositions but rather as dispositions. In other words, though not everyone is in possession of the knowledge or understanding which these innate ideas carry, in the correct context everyone can come to understand certain propositions. Locke argues that, taking the dispositional approach, any attempt to distinguish innate ideas from other propositions which one might hold to be true has been dissolved.


“Then, by the same Reason, all Propositions that are true, and the Mind is ever capable of assenting to, may be said to be in the Mind, and to be imprinted: since if any one can be said to be in the Mind, which it never yet knew, it must be only because it is capable of knowing it; and so the Mind is of all Truths it ever shall know.”


Thus, the limits of understanding for Locke are found not within the mind, but through experience. Locke is perhaps best known for his view of the mind as a tabula rasa, or blank slate. For Locke, as for many empiricists, the complication with this pleasingly simple take on the mind is that the mind must have certain faculties of perception and processing which, logically, cannot themselves be learned through experience.


John Locke’s Solution: The Aggregation of Simple Ideas

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Frans Hals’ portrait of René Descartes, 1625-1649, via RKD (Rijksbureau voor Kunsthistorische Documentatie).


Using Descartes’ concept of the idea, but denying that such ideas are found innately, John Locke then develops a theory of knowledge which explains how all of our ideas are ultimately drawn from experience. By way of experience, we acquire simple ideas, which correlate with the simplest forms of perception. The process of understanding is then one of putting together these simple forms; combining simple ideas into complex ones, holding several simple ideas in mind at once (and therefore, presumably, bringing to mind resonances or contrasts among the ideas and qualities of said ideas), and drawing general propositions by abstraction from these particular ideas. The limits of understanding for Locke are therefore the limits of perception and our processing faculties, and the question of just where those limits fall would become the major preoccupation of philosophers now placed in the same British Empiricist tradition.

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By Luke DunneBA Philosophy & TheologyLuke is a graduate of the University of Oxford's departments of Philosophy and Theology, his main interests include the history of philosophy, the metaphysics of mind, and social theory.