No Innate Knowledge
Locke opens the Essay with an attack on the notion of innate knowledge. He is particularly keen on demolishing the nativist position because it had recently gained renewed currency among intellectual circles, partially in response to Rene Descartes' philosophy. Descartes believed that inborn in our minds are certain mathematical ideas (such as the ideas of geometrical shapes), metaphysical ideas (such as the idea of God and of essences), and eternal truths (such as the truth that something cannot come from nothing).
Locke could not have disagreed more, and he spends the entire first book showing us why. He begins by attacking the possibility of innate principles, such as the principle whatever is is. He then moves on to attack the possibility of innate ideas, such as the idea of God and of infinity. Locke only wages this second attack in order to cover all of his bases. The meat of the argument against innate knowledge rests on an argument against innate principles, since only principles (statements of fact), and not ideas (which are the building blocks of these statements of fact, the sort of things that have names, such as "God," "Man," "blue," "existence"), can properly be called "knowledge." I can know (conceivably) that God exists, I cannot know that "God."
The structure of the argument against innate principles is very simple and can be summed up in three sentences. (1) If, in fact, there are any innate principles, then everyone would assent to them. (2) But there are no principles to which everyone assents. (3) Therefore, there are no innate principles. Locke, however, takes a long time making this simple argument because he is meticulous in establishing that there are no principles to which everyone would assent. His proof of this claim takes the form of a dialectic. He formulates a strong nativist position, objects to it, revises the nativist position, objects, and so on until the position left to the nativist is so weak as to be utterly trivial.
Empiricist Theory of Ideas
As an empiricist, Lock believes that all of our knowledge comes from experience. He further holds that all of our knowledge is built from ideas (think of ideas as little building blocks and knowledge as the structures we create out of them). Taking these two commitments together, he concludes that all of knowledge can be accounted for by accounting for the origin of our ideas. Therefore, Book II, which is all about Locke's theory of ideas, is perhaps the most important part of the Essay.
According to Locke there are two and only two sources for all the ideas we have. The first is sensation, and the second is reflection. In sensation, much as the name suggests, we simply turn our senses toward the world and passively receive information in the form of sights, sounds, smells, and touch. In this way, we receive such ideas as "blue," "sweet," and "loud." In reflection, on the other hand, we turn our mind on itself, and, again passively, receive such ideas as "thought," "belief," "doubt," and "will."
Perhaps the most important issue regarding Locke's theory of ideas is the question of what role an idea is supposed to play in the act of perception. According to the way most people understand Locke, the idea is actually the object of perception. A tree in the external world causes an idea, and this idea, not the tree itself, is what I perceive. This might seem very strange; it is natural to assume that when I have a perception of a tree the object of my perception is the tree. Nonetheless, the majority of philosophers have taken Locke to be saying just this, and there is much evidence to support them. This view of ideas, called the veil of perception because it posits a veil of ideas between us and the world, is still held by many contemporary philosophers of mind.
Distinction Between Primary and Secondary Qualities
In Book II Locke distinguishes two very different relations that can hold between an idea and a quality out on the world. Our ideas of primary qualities (size, shape, and motion) resemble the qualities actually in the world; there really is such a thing as shape, size, and motion in the objects we perceive. Our ideas of secondary qualities (color, smell, taste, and sound) do not resemble any qualities in the world. In actual objects there is only size, shape, and motion, and the arrangement of invisible corpuscles somehow causes in us the sensation of such things as color, taste, and smell.
The most accurate way of stating this distinction is in terms of explanation. In order to explain why a piece of wood looks square to me (even if the wood is in fact trapezoidal, and the appearance of squareness is merely an optical illusion), I must refer to shape. An explanation would go something like this: "The wood is shaped like a trapezoid, but because of where I am standing the angles appear so and so." Shape in the external world is always the cause of my sensation of shape, even if the shape out in the world is not exactly the shape I perceive it to be. On the other hand, color in the external world is never the cause of my sensation of color. The size, shape, and motion of insensible particles cause the sensation of color. In explaining why a flower looks blue, there is no reference to blueness out in the world, only to the size, shape, and motion of pieces of matter.
Locke's primary argument for this claim rests on what he calls the "best science of the day": Boyle's Corpuscular Hypothesis, in which all events and states of the natural world can be explained in terms of the motion of tiny indivisible particles of matter called corpuscles. Given this view of the world, all of our sensation can be explained in terms of size, shape, and motion. There is therefore no reason, Locke claims, to assume that there is anything but these qualities in the external world and so we should not make such an assumption. An argument like this one, which rests on the claim that there is simply no need to posit something (rather than on any conclusive proof that the something in question does not exist), is often referred to as an *argument from parsimony*.
Abuses of Language
Locke's primary concern in Book III is clearing up abuses in language. He thinks that these abuses pose a threat to natural philosophy by ensuring that obscure terms such as "essence" continue to get bandied about and taken seriously, despite the fact that they are utterly incoherent and meaningless as they are currently used. Locke feels that this stubborn adherence to incoherent terms is hindering the acceptance of real scientific progress.
In order to eradicate the abuses of language, Locke first develops a general theory of how our words get their meaning. Then he breaks down types of words, category by category, and shows how we should and should not be using such kinds of words.
Words, Locke claims, refer to ideas. If there is not a clear idea to which our word refers, we should not use that word. In addition, we must take caution to ensure that the ideas to which we refer our words are similar to the ideas to which others refer the same words. Defining our terms and sticking to strict policies of usage are important means by which we can ensure that language does not lead us astray.
Real and Nominal Essence
Scholastics spoke about essences as those properties which make things the sort of things that they are. Essences, for them, were an obscure and complex matter. Locke attempts to show in Book III that our abstract general ideas are what really do this work of sorting particular things into classes. Essences, which caused so much consternation for so long, are nothing but general ideas of the mind.
These general ideas are formed by gathering together ideas of particular things and attending to the similarities among these things. For instance, to form the idea of "cat" I would take my ideas of Frisky, Snowball, Felix, and Garfield and abstract out the tail, the furriness, the size, the shape, the meow etc. I would take all of these similar observable properties and forge them into a new idea, the idea of "cat." This new general idea is what determines what in the world counts as a cat. If an animal fits my idea, then it is a cat. If it does not, then it is not.
This method of individuating sorts makes categories entirely conventional rather than natural. Locke believes that there are no natural kinds in the external world. Instead, there is a continuum of nature, and we impose boundaries among chunks of this continuum for our own purposes.
Locke calls the essence that is responsible for sorting individuals into classes the nominal essence. The nominal essence, again, is just the abstract general idea, which is just a collection of observable properties. In addition to the nominal essence, objects also have a real essence. The real essence of a thing is based in its internal constitution. The real essence is that part of the internal constitution that gives rise to the observable qualities that make up the nominal essence.
Though a real essence has a basis in the world, rather than just in our minds, Locke argues that it cannot be used to sort things into natural kinds. This is so because, first of all, we cannot observe the internal constitution of things. In addition, even if we could observe the internal constitution of things (say, with a powerful microscope) real essences still could not help us sort things into classes. The real essence is itself determined by the nominal essence. Internal constitutions give rise to a myriad of observable properties. It is only the parts of the internal constitution that gives rise to those properties included in the nominal essence that become a part of the real essence. What counts as the real essence, then, is based entirely on how we carve up nominal essences.
The Limits of Human Knowledge
The entire Essay builds up to Locke's theory of knowledge. The upshot of this theory is that knowledge is possible but limited. He is arguing here primarily against the rationalists, who believed that our capacity to know is virtually limitless, and the skeptics, who believed that we are incapable of knowing anything at all.
Locke gives a strict definition of knowledge, whereby one can only be said to know something when one sees why it is necessarily so. That is, knowledge depends on the perception of a necessary connection. This is much the same definition of knowledge that Descartes and the other rationalists used, but in Locke's empiricist hands, it has very different consequences for the human capacity to know.
According to the Cartesian Rationalists, the entire world is made up of a web of necessary connections that the mind, with its use of reason, can potentially unravel. Locke, however, does not believe either of these claims. First of all, he denies that the mind is capable of grasping every necessary connection there is because he thinks that our only source of information is experience and experience does not reveal all the necessary connections to us, as these lie in the unobservable underlying microstructures of object. In addition, he does not believe that there is a necessary connection behind every question; there is no necessary connection linking the unobservable microstructures to the secondary qualities we experience. There is no reason, for instance, why the microstructure that currently gives rise to our sensation of yellow had to give rise to our sensation of yellow, rather than our sensation of blue. The connection between the microstructure and the sensation it produces in us is based entirely on the arbitrary decision of God.
Since all of our access to the natural world is founded on observable properties and we cannot grasp the necessary connections that account for these (or, in the case of secondary qualities, not account for them), Locke concludes that we cannot have any knowledge regarding the nature of things. This is tantamount to saying that science (other than the purely mathematical sciences and the science of morality) can never result in knowledge.
More main ideas from Essay Concerning Human Understanding
John Locke was never the type of philosopher content to sit in an ivory tower or think from the comfort of his armchair. He constantly forced himself into the fray of politics, religion, and science, and the late 17th century was an important time on all these fronts. In politics and religion, it was the time of the Restoration, with bloody skirmishes between crown and parliament, Pope and Anglican Church. In science it was a time of upheaval as well, as a few forward- looking men enthusiastically replaced a vague and slightly spooky Aristotelian picture of the world with a purely mechanical one, in which all of nature could be explained through the motion of matter. Locke's writings proved influential in all of these areas, furthering the cause of religious toleration, contractual rule, and the new mechanistic science.
John Locke was born in 1638 to a family of minor Somerset gentry. His father supplemented the income from his land by working as an attorney and a minor government official. Based on his family's good connections, Locke was able to secure entry to the Westminster School and, from there, to Oxford University. At Oxford he was subjected to Scholasticism, the Aristotelian-influenced course of study that had dominated scholarship since the Middle Ages. He quickly discovered that he had little taste for the dialectical method and the preoccupation with logical and metaphysical subtleties. Completing only the coursework he needed to get by, he turned his intellectual energies to extracurricular endeavors, specifically to politics and medicine.
While still at college Locke published three political essays, two on the topic of religious toleration (at that time he was against it, but he would soon drastically change his position) and the other on natural law theory (again, adopting a position he would later repudiate). These interests (if not the views he held in reference to those interests) would stay with him throughout his life and ultimately be the source of two of his most important works: The Two Treatises on Government and the Essay Concerning Toleration.
Locke's medical studies eventually led him to an interest in chemistry, a fascination that was soon reinforced by an acquaintance with the scientist Robert Boyle. Boyle was one of the new mechanistic scientists, developing a view called the Corpuscularian Hypothesis. According to his theory, all of nature was composed of tiny indivisible bits of matter called "corpuscles," and it was the arrangement and motion of these corpuscles that gave rise to the observable world. In Boyle's home, Locke met many of the leading figures of the new science and became a strong proponent of their views. Compared to the obscure Scholastic picture of the world he was being forced to study in his classes, the simple, intelligible model of nature that Boyle and his friends were propounding was extremely appealing to the young university student.
In 1666 Locke met Lord Ashley, soon to be Earl of Shaftesbury, and became his secretary, his physician, and his son's tutor. Locke moved from Oxford to Ashley's home in London, where he would remain for many years. While living with Ashley, Locke's many intellectual interests transformed from purely academic fascinations to practical endeavors. Ashley himself was a key advisor to King Charles II, and so Locke was afforded an insider view of the political situation, a view that left him with much to say. During this time he published the Essay Concerning Toleration, as well as several treatises on economics. His friendship with a physician named Thomas Sydeham allowed him to explore his medical interest through clinical experience. Finally, his interest in science went from the purely theoretical to the experimental, since Ashley happened to have a chemistry lab in the house. (Chemistry, believe it or not, was a fashionable hobby at the time.)
Around the year 1671 Locke began to write the Essay Concerning Human Understanding. It was his first and only attempt at epistemology. Locke spent 18 years writing the first edition of the book, and he would revise it until his death, publishing a final fifth edition posthumously. Crucial to the development of the Essay was a three year visit to France, which Locke began in 1675. While there, he read much of the work of Rene Descartes and was impressed with his anti-Scholastic, pro-new science philosophy. (Descartes himself had developed a particular version of the mechanistic science.)
When Locke finally returned to England, he found the country in a state of crisis, and his own position in it especially uncertain. Ashley had led a revolt against Charles II and, faced with charged of treason, had fled to Holland. For the next four years Locke concerned himself primarily with politics. Then, when some associates of his were discovered to be plotting the assassination of King Charles and his brother James, he too was forced to flee. It is not clear to what extent Locke himself was involved in this plot, but he must have known enough to consider himself in real personal danger. In 1683 he left for Holland. Soon after, the King asked the Dutch government to extradite Locke back to England, and the philosopher was forced to go underground.
While in exile in Holland, Locke focused his energies primarily on the Essay. In 1688 William of Orange led the Glorious Revolution, and Locke was able to return to England. In 1689 he published the Essay Concerning Human Understanding and the Two Treatises on Government. Locke lived out the rest of his days quietly, pursuing his varied interests. When he died, in October of 1704, he had just completed the notes for the fifth edition of the Essay, and was still at work on three books concerning religion and politics.
Locke was very much a man of his times, and, in part, this was because he did so much to shape them. He was born into an England on the brink of enlightenment, and he helped push the nation over the edge. By the late 17th century, the belief in reasonable religion and secular values were overtaking a blind confidence in authority; individual freedoms were taking central stage in political debates; and excitement over modern technologies and abilities were beginning to replace a worshipful focus on the ancient world. Locke embraced each of these trends and became their most influential spokesman.
The political scene of Locke's maturity was unstable at best. In the wake of civil war, Oliver Cromwell had brought temporary peace. With Cromwell gone by the mid-17th century, however, Parliament and Crown reentered an ardent struggle for power. Because Lord Ashley, Locke's employer, was first the right hand man of King Charles II and then the leader of his opposition in Parliament, Locke found himself at the center of political maneuverings and intrigue. He helped to frame the constitution for the colony of Carolina and wrote the treatises that justified the Glorious Revolution, in which William of Orange seized the throne from King James, Charles' brother. Locke's two Treatises of Government, published anonymously, argued that the only justified government was one that ruled contractually rather than by the ruler's whimsy, thus laying the foundation for a limited kingship, heavily tethered by Parliament and the will of the people. (Years later the insurgent colonists in America would use Locke's arguments as the basis for their own revolution, claiming that King George had failed to abide by his contract, thereby forfeiting his right to rule over them.)
Locke was also extremely active in religious affairs. A heated Protestant/Catholic divide helped to make the stormy political scene of late 17th England even more turbulent. Issues of religious intolerance and forced conversion were of paramount practical importance. Locke began his career on the side of authoritarian religious impositions, but quickly changed his mind. A 1675 visit to Cleves, which exposed him to a community where members of different churches lived together peacefully, might have helped sway his opinion toward religious toleration, in favor of which he wrote several well-read and enormously controversial essays. Locke's religious writings, as well his publication of the Essay, landed him in a lengthy disagreement with the Bishop of Worcester. Some material generated from their published debates found its way into later editions of the Essay.
Locke's participation in modern scientific advances was largely the result of his close ties with Robert Boyle. Throughout Europe the dominance of the Universities, with their focus on the ancient world, was being challenged by thinkers who preferred to focus on new technology and modern ideas. Locke's Essay gave one of the decisive blows to the already ailing Scholastic movement.
The Essay Concerning Human Understanding is the only work on epistemology and metaphysics in a lifetime collection dominated by religious and political writings. There is no indication that Locke showed any interest in epistemology prior to 1671, electing instead to focus his energies on questions of politics, religion, and science. In a famous paragraph in the Essay's, "Epistle to the Reader," Locke explains what drew him suddenly to the study of human understanding: while discussing an unrelated subject with friends (he does not mention what this subject was), he came to the conclusion that no significant headway could be made in any field until there was an understanding of understanding itself, in particular of its capacities and limits. Therefore, he set out to determine what we could and could not hope to understand by analyzing the human mind and the nature of knowledge. The Essay can be read as an attempt to ground all of Locke's further inquiries into politics, religion, economics, education and the like, by drawing the boundaries that demarcate where a search for answers should begin and end.
The philosophy Locke presents in his Essay is best understood as a direct response to the two schools of philosophical thought dominating the intellectual scene of the late 17th century: the Aristotelian-influenced Scholasticism, which had ruled the Universities since the Middle Ages, and the Cartesian rationalism, which was challenging Scholastic authority with a radical new picture of how the mind comes to know. Locke wanted to chart a middle course between these two views, one that retained the positive features of each. The Scholastic picture of how the mind works can be summed up the phrase "nothing in the intellect, not first in the senses." Scholastic philosophers, following Aristotle, believed that all of our knowledge comes through our sense organs. They were empiricists, like Locke. However, their empiricism was of a very naïve form; they believed that our senses are incapable of systematically deceiving us about the kinds of things that are in the world. If the senses tell us that there are colors, then there are colors. If the senses tell us that there are enduring objects, such as tables and chairs, then there are enduring objects. The trustworthiness of the senses was built into the theory of how perception operated: on this view, the perceiver took on the form of the thing perceived and became, in a very obscure sense, like the object of perception.
Rene Descartes, in his Meditations of First Philosophy, attempted to revolutionize epistemology. If the Aristotelian view can be summarized as "nothing in the intellect, not first in the senses," Descartes' position can be summed up as "no trusting the senses until they have been verified by the intellect." Descartes believed that the senses systematically deceive us, and that it is only by properly utilizing our faculty of reason that we can come to know the world. Like the other rationalists who came after him, such as Baruch Spinoza and G. W. Leibniz, Descartes believed that the entire natural world is explicable in terms of a chain of logical connections, and that all we need do is use our reason to trace these connections to know everything there is to know.
Descartes' primary reason for asserting that the senses systematically deceive was his commitment to the new mechanistic science, which conflicted with the Scholastic conception of the natural world. On the Scholastic view, the most basic units of existence were substances, and these came in an innumerable variety, each with their own distinct essence, the thing that made them what they were. All substances were composed of some mixture of the four elements: earth, air, fire, and water. To explain why anything happened in the natural world, the Scholastic would appeal to these four elements and the four primary qualities by which they were characterized - hot, cold, wet, dry.
Descartes simplified this picture considerably. He too called the basic units of existence substances, but for him substances came in only three types, rather than in an innumerable variety. There was God, there were minds, and there were bodies. The essence of mind was thought, while the essence of body--of matter, of the natural world, of all we see around us--was extension. By making extension the essence of body, Descartes was able to simplify the study of the natural world: it no longer involved the complex and obscure charting of primary qualities flowing in and out of elements. Instead, the study of the natural world was simply the study of geometry.
This was where Descartes' new epistemology came in. The natural world that he posited--one that was explicable exclusively in terms of the size, shape, and motion of matter--sounded nothing like the world our senses represent to us. We perceive a world filled with things like color, odor, and sound and see nothing to indicate that the essence of body is extension. Descartes' solution to this apparent problem was to give more power to the intellect and less to the senses. On his view, we come to understand the world not by observing it, but by reasoning about it, starting from ideas innate to the human mind. It is by reasoning with these innate ideas, he claimed, that he arrived at the discovery that the essence of body is extension, and it is by reasoning that we can come to know everything else about the way the world really is.
Like Descartes, Locke, was a proponent of the new science. He too believed that the natural world was explicable exclusively in terms of shape, size, and motion of matter, though the particulars of the view he ascribed to were somewhat different from the Cartesian picture. (Whereas Descartes believed that all matter was continuous, Locke ascribed to Boyle's Corpuscular Hypothesis, according to which the natural world is composed of indivisible bits of matter called corpuscles.) He had to admit, therefore, that Descartes was right about that the senses do systematically deceive us.
Locke, however, resisted accepting Descartes' epistemology because he held, like the Scholastics, that nothing came into the mind except via the senses. The Essay, therefore, is an attempt to reconcile his empiricism with his commitment to the new science. His aim was to defend an empiricist model of the mind, while clearing the way for new ideas about the nature of reality.
The attempt had never been made before, but once Locke began the search for a plausible empiricism, one consistent with science, has never really ended. George Berkeley and David Hume made the first significant endeavors after Locke, building on the foundation that their predecessor had so meticulously laid. In the 20th century the Logical Positivists gave it a worthy shot as well, as did their nemesis W.V. Quine. Empiricism has, to a certain extent, fallen out of fashion as of late, but epistemology is still largely guided by the questions originally posed by Locke and his empiricist followers.