Experience and the limits of understanding › The Architecture of the Essay

The work has four books. Book I argues against innate principles and ideas. Book II examines ideas and their origins. Book III examines words. Book IV examines knowledge and opinion. That sequence keeps two questions separate: possessing an idea does not itself establish that a belief involving it is knowledge. ## Book I: Tearing Down Innate Ideas Locke first tests the appeal to universal agreement. Even if everyone assented to a principle, that would not by itself show it was innate: agreement could have another explanation. He then argues that the proposed logical maxims do not, in fact, enjoy the universal conscious recognition claimed for them. His examples include the principles "Whatsoever is, is" and "It is impossible for the same thing to be and not to be." Locke points to children and people he describes, in the terminology of his period, as lacking awareness of these propositions. The argumentative question is whether a truth can count as already known when the person has never apprehended it. ::: {.callout-warning title="Common Misconception"} Locke distinguishes a natural capacity to acquire knowledge from a proposition already present as knowledge. His objection is that the first does not establish the second. An account of learning still has to explain how a person comes to apprehend the proposition. ::: He also contests claims of universal assent to moral principles. Book I, chapter III appeals to differences in reported practices and moral judgments. These are Locke's arguments and historical reports, not a license to accept every report he repeats as reliable anthropology. Their intended role is to challenge the claim that a single set of practical principles is consciously acknowledged by everyone. Locke anticipates the reply that innate principles become known when people reach the use of reason. He asks why learning a proposition through reasoning should prove it was previously inscribed in the mind. The capacity to discover something, on his account, is not evidence that the discovered content was already known. ## Book II: Building Knowledge from Experience ::: {.callout-note title="Simple Ideas"} Simple ideas are the elements of thought that the mind receives without being able to make or divide them at will. Locke's examples include particular colors and tastes. The mind can combine the materials supplied by experience, but it cannot invent a wholly new simple idea by merely deciding to do so. ::: Having cleared the ground, Locke constructs his positive theory. All ideas, he argues, come from one of two sources: sensation and reflection. Sensation supplies ideas through the senses. Looking at a red apple, touching its skin, and tasting it illustrate different sensory contributions. The apple example is a way to follow Locke's distinction: the resulting sensory ideas are materials for thought, while the idea of the apple as a substance is more complex. Reflection is the mind's awareness of its own operations. When you notice yourself thinking, doubting, believing, willing, or remembering, you gain ideas of these mental activities. Reflection is, as Locke puts it, "internal sense": the mind perceiving its own workings. From these two sources (and only these two sources) all ideas arise. But how do we get from simple sensations to the rich conceptual life we actually have? Locke's answer involves the mind's active powers of combination, comparison, and abstraction. Locke illustrates complex ideas with substances such as gold: a collection including yellowness, weight, malleability, and fusibility. The mind puts such ideas together, but our observed collection does not amount to knowing the substance's underlying constitution. The complex idea gathers what we associate with gold; it need not reveal why those properties occur together. ::: {.callout-note title="Primary and Secondary Qualities"} Primary qualities, such as solidity, extension, figure, and motion or rest, belong to bodies. Secondary qualities are powers in bodies to produce sensations such as colors and tastes in perceivers. The power is in the object; the resulting idea is in the mind. Calling secondary qualities powers avoids treating Locke as if he denied that objects have them. ::: Locke says our ideas of primary qualities resemble qualities in bodies. Our ideas of secondary qualities do not resemble the powers that cause them. A snowball's whiteness and coldness are sensations in us; the snowball has powers to produce those sensations through its material constitution. The distinction is between a sensation and the object's power, rather than between a real property and sheer nothingness. This is a philosophical account of perception, not a conclusion we should substitute for modern physical explanations. Within Locke's account, the same object can produce ideas that do not resemble its underlying material qualities. The practical reading task is to keep the object, its power, and the perceived idea distinct. ## Book III: Language and Its Pitfalls Book III turns from ideas to words. Locke argues that words are sensible signs people use to communicate their ideas. That creates a difficulty: a shared sound does not guarantee that speakers attach the same idea to it. Words, Locke argues, are signs for ideas. The word "gold" stands for a complex idea in my mind: a combination of simple ideas I have associated with that substance. When I use the word in conversation, I am attempting to trigger a similar idea in your mind. My idea of gold and your idea of gold might differ because we associate different collections of properties with the word. Locke treats uncertain or inconsistent uses of words as a source of dispute. Before deciding whether we disagree about an object, we may need to establish what each speaker means. ::: {.callout-tip title="Practical Application"} Try the distinction on a disagreement about what is "fair." Ask each speaker to explain the idea attached to the word and give an example. This is a reading exercise inspired by Locke's account, not a promise that defining a word will resolve the underlying disagreement. ::: Locke does not reject abstract general terms as such. In Book III, chapter III, general words become useful through abstract ideas. His criticism concerns their abuse: words used without determinate ideas, or used as if a nominal essence disclosed a substance's real constitution. His distinction between nominal and real essences is especially important for names of substances. For reading the *Essay*, this gives us a useful discipline: distinguish a discussion about the meaning of a term from a discussion about what exists. A definition can settle how we will use a word without establishing every claim about the thing named. ## Book IV: The Scope and Limits of Knowledge ::: {.callout-note title="Knowledge as Perception of Agreement"} For Locke, knowledge means perceiving how ideas relate to each other. When you know that two plus two equals four, you perceive the agreement between the idea of "two plus two" and the idea of "four." Knowledge is this act of mental perception, not mere belief or opinion. ::: In the final book, Locke turns to epistemology proper: what can we actually know, and how certain can we be? His answer is sobering. Genuine knowledge, he argues, is the perception of agreement or disagreement between ideas. When I know that white is not black, I perceive the disagreement between these two ideas. When I know that a triangle has three sides, I perceive the agreement between the idea of "triangle" and the idea of "three-sided figure." Locke identifies three degrees of knowledge, ranked by certainty. Intuitive knowledge is the most certain: immediate perception of agreement or disagreement without any intermediate steps. That I exist, that white is not black, that a circle is not a triangle: these are intuitive certainties. Demonstrative knowledge comes next. Here we perceive agreement or disagreement through a chain of intermediate ideas, each step of which is intuitively certain. Mathematical proofs are the paradigm case: each step is intuitive, and the chain leads us to conclusions we could not have seen immediately. Sensitive knowledge concerns the present existence of particular external things through sensation. Locke regards it as less certain than intuition or demonstration, but still beyond mere probability. He considers dreaming objections in Book IV, chapter XI, and argues that actual sensation provides the assurance appropriate to this kind of knowledge. Locke distinguishes knowledge from judgment that proceeds on probability. Much of life requires assent where we lack the perception of agreement that constitutes knowledge in his strict sense. Book IV therefore examines degrees of assent and the evidence on which judgment should depend. Limited knowledge does not mean that every uncertain belief deserves the same confidence.