An Essay Concerning Human Understanding | Study Guide

John Locke

Download a PDF to print or study offline.

Study Guide
Cite This Study Guide

How to Cite This Study Guide

quotation mark graphic


Course Hero. "An Essay Concerning Human Understanding Study Guide." Course Hero. 9 May 2018. Web. 12 Dec. 2018. <>.

In text

(Course Hero)



Course Hero. (2018, May 9). An Essay Concerning Human Understanding Study Guide. In Course Hero. Retrieved December 12, 2018, from

In text

(Course Hero, 2018)



Course Hero. "An Essay Concerning Human Understanding Study Guide." May 9, 2018. Accessed December 12, 2018.


Course Hero, "An Essay Concerning Human Understanding Study Guide," May 9, 2018, accessed December 12, 2018,

An Essay Concerning Human Understanding | Main Ideas


Blank Slate

In Book 1 Locke lays out the basis of his empiricist view of knowledge (see Context): his belief that the human mind brings no innate ideas with it into the world. The concept of a mind without innate ideas is popularly known as tabula rasa, the Latin phrase meaning "blank slate." Locke, however, never actually uses that phrase in Latin or English. Instead, he calls the mind "white paper, void of all characters" (Book 2, Chapter 1). Nonetheless, the term tabula rasa has remained a popular way of referring to this idea. In proposing the blank-slate model of the human mind, Locke sets himself in opposition to philosophical nativists, who insist on the existence of at least some innate ideas.

The claimed absence of innate ideas has serious consequences for Locke's arguments in Books 2 through 4. Since the mind, he believes, has nothing "engraved" on it before birth, everything—including such deeply held convictions as a belief in God—must be acquired through experience. Accordingly, he spends much of Book 2 simply enumerating different kinds of ideas and showing how they could, in principle, arise empirically. Sometimes the route from experience to idea is fairly direct, at least from Locke's point of view. A person with typical color vision sees apples, roses, and sunsets, and the concept of "red" is—to use the slate analogy—written on the mind for later use. In more obviously complicated cases, Locke has to do a great deal of explaining. For example, to show how an idea like "murder" arises in the mind, Locke must show (or at least suggest) how ideas of "killing," "premeditation," and so on come about. Nonetheless, Locke stands firm in his argument. Any idea the mind is capable of formulating, he maintains, can be obtained through experience.

The "blank slate" hypothesis also implies some sobering restraints on human knowledge. In Locke's account, knowledge of any kind has just two ways of getting into the mind. The two "inlets" are sensation—sensory experience of the outside world—and reflection, meaning the mind's awareness of its own thoughts. Sensation is mainly useful for giving us the basic building blocks with which to form more complex thoughts. Reflection, as Locke uses the term, is similar to what a psychologist or cognitive scientist today would call metacognition. It is not just thinking, but "thinking about thinking."

The limitations of these two inlets become, in effect, the outer limits of our collective understanding. If we can't discover something from direct sensory experience, or infer it from our own thought processes, we can't truly know it at all. Even seemingly mundane things, like the time the train will arrive or the chemical makeup of table salt, are essentially unknowable from this perspective. We can read in a timetable that the train will arrive at 8:08 a.m., and we may have seen it arrive at 8:08 many times before, but we can't know for sure that it will arrive on time today. In trying to predict even a boring part of the immediate future, we drift away from certain knowledge and into conjecture. Many of the topics Locke finds most interesting, such as the nature of God and the spiritual world, also seem to fall into this category. They are inaccessible to sensation and reflection, setting them outside the boundaries of our understanding.

What We Don't Know

For a work devoted to knowledge and understanding, Locke's Essay spends a remarkable amount of time discussing ignorance. Book 2 concludes with five chapters on how our ideas can go awry, becoming false, obscure, confused, or "fantastical." Book 3 includes a section on the shortcomings and abuses of language, which hinder our communication of even the imperfect ideas we do have. Book 4 proclaims, loud and clear, that in many important areas of life we cannot have certain knowledge at all. The best we can do is to weigh the probabilities.

The point of all this, Locke assures the reader, is not to make people lazy or despondent. Rather, Locke views an awareness of humanity's limitations as an important step in the ongoing quest for knowledge. In his opening chapter he warns readers not to "boldly quarrel with their own constitution, and throw away the blessings their hands are filled with, because they are not big enough to grasp everything." In other words, we shouldn't presume that human knowledge is unlimited, but neither should we give up the search altogether. The trick is to make the most of our abilities in the areas where our knowledge pays off—and not to waste time in areas that are "above reason." The cause of knowledge suffers, Locke says, when humanity fails to match its aims to its abilities.

Locke's view of the limits of human knowledge is closely related to his empiricism. Unlike the nativists, he does not believe God has provided human beings with a "starter kit" containing basic logical propositions or spiritual truths. Instead, everything has to be figured out from scratch. Locke makes no secret of the rough-and-ready, "homemade" quality that ideas have as a result. In Book 2, Chapter 1 he uses a striking metaphor to describe this characteristic. Ideas in an actual human mind, he says, have a "tang of the cask," a term which usually refers to the off-flavors found in cask-aged beverages like wine and whiskey. That is, human ideas have the characteristics one would expect given that they are acquired through sensory experience and an imperfect reasoning process. They lack the pure and ethereal nature of ideals as described by Plato. They are neither as clear nor as consistent as the "maker's mark" that Descartes imagines God imprinting on the human mind.

In fact, Locke candidly admits that different people's idea of God—if they have one at all—will vary considerably. Some people embrace the notion of multiple deities, which Locke finds absurd, but which he nonetheless acknowledges as an idea of God. Others conflate their notion of God with a part of the natural world, such as the sun, the sky, or the earth. People in Locke's culture (i.e., early modern Britain) generally agree that God is omnipotent, but they often disagree about what that means. For Locke, all this is grist for the empiricist mill. If people can have such diverse notions of God, he asks, why should we believe that there is one overriding God-idea shared by all human minds? As it happens, Locke's disavowal of innate ideas of God was one of the more controversial parts of the Essay. Many, including Leibniz (see Context) took issue with Locke's hesitation to give a stronger opinion on this subject.

Personal Identity

Locke also makes some important claims concerning the nature of personal identity. This topic is treated primarily in Book 2, Chapter 27, where Locke proposes a sharp distinction between a "man" (what we would today describe as a "human being") and a "person." A "man," Locke says, is defined as an individual by a "continued life" in the same "organized living body." The physical particles making up that body change all the time, but the organization remains recognizably the same. Thus, even if two people somehow shared a soul, they would nonetheless constitute different "men" in Locke's view.

"Person," for Locke, is a different concept, one of special relevance in law and morality. Locke defines a person with reference to the ongoing nature of consciousness. If a soul could somehow be shown to have reincarnated with its memories intact, it would count as "the same person" across its different incarnations. Yet as Locke points out, most people who claim to have undergone reincarnation cannot recall anything of their alleged past lives. Consequently, whether or not reincarnation has actually taken place, the soul is a different person in this life than it was in the past.

Thus in Locke's analysis, remembering defines a person as an individual, and forgetting—if profound and complete enough—can disrupt personal identity. At its most extreme this can create a situation in which there are effectively two persons, whom we might call the "before" and the "after." If a man were to lose his memory completely, Locke argues, he would become a new person, fundamentally different from the person he was before. (He would still, according to Locke's earlier definition, be the same man.) God, knowing the man had no recollection of his prior deeds, would not be so unjust as to reward or punish him for those forgotten actions. Likewise, a truly just legal system would not hold a person accountable for actions they no longer remember. The person the courts might wish to punish is, from Locke's point of view, already gone.

Locke admits that this definition of personhood is hard to implement in a legal system. When people claim to have forgotten what they did while drunk, for instance, the law still punishes them for any crimes committed. Locke says this is because of the difficulty of proving that the illicit acts were really forgotten. The law cannot look inside an accused arsonist's head and determine that there is no mental record of drunkenly burning down the neighbor's barn. Rather, Locke asserts, the legal system must presume by default that people remember their past actions and are to be held responsible for them.

Cite This Study Guide

information icon Have study documents to share about An Essay Concerning Human Understanding? Upload them to earn free Course Hero access!