An Essay Concerning Human Understanding Analysis

John Locke’s An Essay Concerning Human Understanding is the first major presentation of the empirical theory of knowledge that was to play such an important role in British philosophy. The author had studied at Oxford, and later he became a medical doctor. Although he did not practice much, he was greatly interested in the developments current in medical and physical science, and there is some evidence that he first began to formulate his theory of knowledge in terms of considerations arising from medical researches of the day. Locke was a member of the Royal Society of England, where he came into contact with many of the important experimental scientists, such as Robert Boyle and Sir Isaac Newton. A discussion with some of his friends seems to have been the immediate occasion of the writing of An Essay Concerning Human Understanding, in which Locke attempted to work out a theory of knowledge in keeping with the developing scientific findings and outlook.

The completed version of the work dates from the period when Locke, along with his patron, the Anthony Ashley Cooper, the third earl of Shaftesbury, was a political refugee in Holland. After the Glorious Revolution of 1688, Locke returned to England and was quickly recognized as the leading spokesperson for the democratic system of government that was emerging in his homeland. The essay, first published in the same year as Locke’s famous work in political philosophy, Two Treatises of Government, quickly established the author as the foremost spokesperson for the new empirical philosophical point of view that was to dominate English philosophy from then on.

The question to which Locke addressed himself in his essay is that of “the origin[s], certainty, and extent of human knowledge, together with the grounds and degrees of belief, opinion, and assent.” By using what he called “this historical, plain method,” Locke hoped to discover where our ideas and our knowledge come from, what we are capable of knowing about, how certain our knowledge actually is, and when we may be justified in holding opinions based on our ideas. The value of such an undertaking, Locke asserted, is that one would thus know the powers and the limits of human understanding, so that “the busy mind of man” would then restrict itself to considering only those questions with which it was actually capable of dealing and would “sit down in a quiet ignorance of those things” beyond the reach of its capacities.

Before commencing his investigations, Locke pointed out that human beings do, in fact, have adequate knowledge to enable them to function in the condition in which they find themselves. Therefore, even if the result of seeking the origin, nature, and extent of our knowledge leads us to the conclusion that we are unable to obtain complete certitude on various matters, this should not be grounds for despair, for skepticism, or for intellectual idleness. People have wasted too much time, Locke insisted, in bemoaning their intellectual situation or in disputing in areas in which satisfactory conclusions are impossible. Instead, he said, we should find out our abilities and our limitations, and then operate within them.

The first book of An Essay Concerning Human Understanding deals with one theory about the origin of our ideas, the thesis that our knowledge is based upon certain innate principles that are supposed to be “stamped upon the mind of man.” Locke severely criticized this theory, especially in the form in which it had been presented by thinkers such as Herbert of Cherbury. Adherents of this theory of innate ideas had maintained that the universal agreement of humankind regarding certain principles showed that these must be innate. Locke argued in opposition that the fact of universal agreement would be insufficient evidence as to the source of the principles in question. He also argued that, in fact, there actually are no principles that are universally agreed to, since children and idiots do not seem to know or believe the principles that are usually cited as examples of innate ideas. The way in which children acquire knowledge about the principles in question, through the learning process, further indicates that they are not born with innate ideas.

After having criticized the innate idea theory, Locke turned next to the positive side of his investigation. We do have ideas (an idea being defined as whatever is the object of the understanding when a person thinks); this is beyond any possible doubt. Then, if the ideas are not innate, where do they come from?

The second book of An Essay Concerning Human Understanding begins the development of a hypothesis about the origins of human knowledge, namely, the empirical theory. Let us suppose, Locke said, that the mind initially is just a blank tablet (a tabula rasa). Where, then, does it obtain its ideas? From experience, Locke proclaimed. Experience comprises two sources of ideas, sensation and reflection. We receive many, if not most, of our ideas when our sense organs are affected by external objects. We receive other ideas by reflection when we perceive the operations of our minds on the ideas that we have already received. Sensation provides us with ideas of qualities, such as the ideas of yellow or of heat. Reflection provides us with ideas such as those of thinking, willing, and doubting. These two sources, Locke insisted, give us all the ideas that we possess. If anyone has any doubts about this, let that person simply inspect his or her own ideas and see if there are any that have not come to him or her either by sensation or reflection. The development of children also provides a further confirmation of this empirical theory of the origin of human knowledge. As the child receives more ideas from sensation, and reflects on them, that child’s knowledge gradually increases.

If these are the types of ideas that we possess, classified according to their sources, can we distinguish those ideas that resemble actual features, or qualities of objects, and those that do not? The qualities of objects are divided by Locke into two categories, the primary and the secondary ones. The primary ones are those that are inseparable from bodies no matter what state the object may be in. This group includes solidity, extension, figure, mobility, and number. In contrast, the secondary qualities “are nothing in the objects themselves, but the powers to produce various sensations in us by their primary qualities,” such as the power of an object, through the motion of its solid, extended parts, to produce sounds, tastes, and odors in us when we are affected by it.

Thus, in Locke’s theory, objects possess primary qualities, the basic ingredients of Newtonian physics, and they possess secondary ones, which are actually the powers of the primary qualities to cause us to perceive features, such as colors, odors, and so on, which are not “in” the objects themselves. In terms of this distinction, we can say that our ideas of primary qualities resemble the characteristics of existing objects outside us, whereas our ideas of secondary qualities do not. The primary qualities of things are really in them, whereas the secondary qualities, as perceived sensations, are only in the observer. If there were no observers, only the primary qualities and their powers would exist. Hence, the rich, colorful, tasteful, noisy, odorous world of our experience is only the way we are affected by objects, not the way objects actually are. This distinction between our ideas of primary and secondary qualities led Locke to argue that some of our ideas give us genuine information about reality, while others do not.

At the end of the second book of An Essay Concerning Human Understanding, Locke evaluated what he had discovered about the nature of our ideas. This evaluation commences the examination of the problem of the extent and certitude of our knowledge, which is developed at length in the fourth book. Our ideas are real, Locke contended, when they have a foundation in nature and when they conform with the real character of things. In this sense, all simple ideas are real because they must be the result of genuine events and things (since the mind cannot create them but receives them from experience). However, not all real ideas are necessarily adequate representations of what does in fact exist. Ideas of primary qualities are both real and adequate. Ideas of secondary qualities are real but only partially represent what is outside us. They represent powers that exist but not features corresponding to the ones that we perceive. The ideas of substances that we have are very inadequate, because we are never sure that we are aware of all the qualities that are joined together in one substance, nor are we sure of why they are so joined. Hence, some of our ideas tell us what is really outside us, whereas other ideas, caused by what is outside us or by our reflection on our ideas, do not adequately represent “real” objects.

Later philosophers, such as George Berkeley and David Hume, were to argue that once Locke had admitted that some of our ideas were neither representative of reality nor adequate to portray reality, he could not then be certain that any of our ideas actually correspond to real features of the world. Hence, they contended that Locke, in trying to build from an empirical theory of knowledge to genuine knowledge of reality, had actually laid the groundwork for a skeptical denial of the contention that people can know anything beyond the ideas in their own minds. Locke’s theory rested on maintaining that our ideas of primary qualities resemble genuine characteristics of reality. However, the opponents argued, primary qualities are really no different from secondary qualities, as we know them, and hence we have no assurance from the ideas themselves that some are real and adequate and others are not.

The third book of An Essay Concerning Human Understanding appears to deal with some unrelated topics, those concerning the nature of words and language. This book, which evoked the interest of those concerned with linguistic philosophy, covers problems normally dealt with in anthropology, psychology, linguistics, and philosophy.

Two points that are raised are of central importance to Locke’s main theme of the nature and extent of our knowledge and played a role in the later history of empirical philosophy. One of these is Locke’s theory concerning the meaning and referrent of general terms, such as “man” and “triangle.” All things that exist, Locke asserted, are particular, but by abstracting from our ideas of things, by separating from them particular details or features, we finally form a general idea. In this way, we arrive at the general abstract ideas about which we reason. Berkeley and Hume both challenged Locke on this point and insisted that we do not, in fact, possess any abstract general ideas. Hence, they insisted that an empirical account of our ideas of so-called general terms must be developed from the particular ideas that we have.

One of the general terms that Locke claimed gained some meaning from the abstracting process is “substance.” However, when he analyzed what we might mean by the term, Locke distinguished between what he called “the nominal essence” and “the real essence” of a substance. The nominal essence is that abstract general idea of a substance formed by abstracting the basic group of features that constantly occur together. The real essence, in contrast, is the nature of the object that accounts for its having the properties that it does. The nominal essence describes what properties a substance has, whereas the real essence explains why it has these properties. Unfortunately, Locke pointed out, we can never know the real essence of anything, since our information, which we abstract from, deals only with the qualities that we experience and never with the ultimate causes that account for the occurrence of these properties. Thus, our knowledge of things is sure to be sharply curtailed because of the fact that we will never discover the reasons why things have the characteristics that they have.

The fourth and last book of An Essay Concerning Human Understanding deals with knowledge in general, with the scope of knowledge, and with the question of how certain we can be of such knowledge. Our knowledge deals only with ideas, since these are the only items with which the mind is directly acquainted. What constitutes knowledge, according to Locke, is the perception of the agreement or disagreement of two ideas. Ideas may agree or disagree in four ways. They may possibly be identical or diverse. They may be related in some respect. They may agree in coexisting in the same subject or substance. They may agree or disagree in having a real existence outside the mind. All of our knowledge, Locke insisted, falls under these headings. We know either that some ideas are the same or different, or that they are related, or that they always coexist, or that they really exist independently of our minds.

If these are the kinds of items that we can know about, how can we gain such knowledge? One source of our knowledge is intuition, the direct and immediate perception of the agreement or disagreement of any two ideas. The mind “sees” that black is not white and that a circle is not a triangle. Also, “this kind of knowledge is the clearest and most certain that human frailty is capable of.” Anyone who demands more certainty than that gained by intuition “demands he knows not what, and shows only that he has a mind to be a sceptic, without being able to be so.” All certain knowledge depends upon intuition as its source and guarantee.