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Locke: The Origin of Ideas

We now leave the Continent for an extended look at philosophy in Great Britain during the seventeenth and eighteenth centuries. Here the favored model for achieving human knowledge was not the abstract mathematical reasoning so admired by the rationalists but the more concrete observations of natural science. Heeding the call of Francis Bacon, British scientists had pursued a vigorous program of observation and experiment with great success. Isaac Newton showed that both celestial and terrestial motion could be explained by reference to a simple set of laws of motion and gravitation; Robert Boyle investigated the behavior of gasses and proposed a general theory of matter as a collection of corpuscles; and Thomas Sydenham began to use observational methods for the diagnosis and treatment of disease.
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Philosopher John Locke greatly admired the achievements that these scientists (his friends in the Royal Society) had made in physics, chemistry, and medicine, and he sought to clear the ground for future developments by providing a theory of knowledge compatible with such carefully-conducted study of nature.

The goal of Locke's An Essay Concerning Human Understanding (1690), then, is to establish epistemological foundations for the new science by examining the reliability, scope, and limitations of human knowledge in contrast with with the pretensions of uncritical belief, borrowed opinion, and mere superstition. Since the sciences had already demonstrated their practical success, Locke tried to apply their Baconian methods to the pursuit of his own philosophical aims. In order to discover how the human understanding achieves knowledge, we must trace that knowledge to its origins in our experience.

Locke's investigation into human knowledge began by asking how we acquire the basic materials out of which that knowledge is composed, our ideas. For Locke, an idea is Essay I i 8) (Note that this is an extremely broad definition: it includes concrete sensory images, abstract intellectual concepts, and everything in between. The colors and shapes I see before me right now are ideas, and so are my hunger, my memories of the ocean, my hopes for my children, the multiplication tables, and the principles of democratic government.) Ideas, then, are the immediate objects of all thought, the meaning or signification of all words, and the mental representatives of all things. Locke's question was, where do we get all of these ideas which are the content of our knowedge?

Ideas from Experience

First, Locke eliminated one bad answer to the question. Most of Book I of the Essay is devoted to a detailed refutation of the belief that any of our knowledge is innate. Against the claims of the Cambridge Platonists and Herbert of Cherbury, Locke insisted that neither the speculative principles of logic and metaphysics nor the practical principles of morality are inscribed on our minds from birth. Such propositions do not in fact have the universal consent of all human beings, Locke argued, since children and the mentally defective do not assent to them. Moreover, even if everyone did accept these principles, their universality could be better explained in terms of self-evidence or shared experience than by reference to a presumed innate origin. (Essay I ii 3-5) Innatism is the refuge of lazy intellectual dictators who wish thereby to impose their provincial notions upon others. Besides, Locke held, our knowledge cannot be innate because none of the ideas of which it is composed are innate.

As the correct answer to the question, Locke proposed the fundamental principle of empiricism: all of our knowledge and ideas arise from experience. (Essay II i 2) The initially empty room of the mind is furnished with ideas of two sorts: first, by sensation we obtain ideas of things we suppose to exist outside us in the physical world; second, by reflection we come to have ideas of our own mental operations. Thus, for example, "hard," "red," "loud," "cold," "sweet," and "aromatic" are all ideas of sensation, while "perceiving," "remembering," "abstracting," and "thinking" are all ideas of reflection. ("Pleasure," "unity," and "existence," Locke held, are ideas that come to us from both sensation and reflection.) Everything we know, everything we believe, every thought we can entertain is made up of ideas of sensation and reflection and nothing else.

But wait. It isn't true that I can think only about what I myself have experienced; I can certainly think about dinosaurs (or unicorns) even though I have never seen one for myself. So Locke's claim must be about the ultimate origin of our ideas, the source of their content. He distinguished between simple and complex ideas and acknowledged that we often employ our mental capacities in order manufacture complex ideas by conjoining simpler components. My idea of "unicorn," for example, may be compounded from the ideas of "horse" and "single spiral horn," and these ideas in turn are compounded from less complex elements. What Locke held was that every complex idea can be analyzed into component parts and that the final elements of any complete analysis must be simple ideas, each of which is derived directly from experience. Even so, the empiricist program is an ambitious one, and Locke devoted Book II of the Essay to a lengthy effort to show that every idea could, in principle, be derived from experience.

A Special Problem

Locke began his survey of our mental contents with the simple ideas of sensation, including those of colors, sounds, tastes, smells, shapes, size, and solidity. With just a little thought about specific examples of such ideas, we notice a significant difference among them: the color of the wall in front of me seems to vary widely from time to time, depending on the light in the room and the condition of my eyes, while its solidity persists independently of such factors. Following the lead of Galileo and Boyle, Locke explained this difference in corpuscularian fashion, by reference to the different ways in which the qualities of things produce our ideas of them.

The primary qualities of an object are its intrinsic features, those it really has, including the "Bulk, Figure, Texture, and Motion" of its parts. (Essay II viii 9) Since these features are inseparable from the thing even when it is divided into parts too small for us to perceive, the primary qualities are independent of our perception of them. When we do perceive the primary qualities of larger objects, Locke believed, our ideas exactly resemble the qualities as they are in things.

The secondary qualities of an object, on the other hand, are nothing in the thing itself but the power to produce in us the ideas of "Colors, Sounds, Smells, Tastes, etc." (Essay II viii 10) In these cases, our ideas do not resemble their causes, which are in fact nothing other than the primary qualities of the insensible parts of things. The powers, or tertiary qualities, of an object are just its capacities to cause perceptible changes in other things.

Thus, for example, the primary qualities of this rose include all of its quantifiable features, its mass and momentum, its chemical composition and microscopic structure; these are the features of the thing itself. The secondary qualities of the rose, on the other hand, include the ideas it produces in me, its yellow color, its delicate fragrance; these are the merely the effects of the primary qualities of its corpuscles on my eyes and nose. Like the pain I feel when I stick my finger on a thorn, the color and smell are not features of the rose itself.

Some distinction of this sort is important for any representative realist. Many instances of perceptual illusion can be explained by reference to the way secondary qualities depend upon our sensory organs, but the possibility of accurate information about the primary qualities is preserved, at least in principle. The botanical expert may be able to achieve detailed knowledge of the nature of roses, but that knowledge is not necessary for my appreciation of their beauty.

Complex Ideas

Even if the simple ideas of sensation provide us with ample material for thinking, what we make of them is largely up to us. In his survey of ideas of reflection, Locke listed a variety of mental operations that we perform upon our ideas.

Notice that in each of these sections (Essay II ix-xii), Locke defined the relevant mental operations as we experience them in ourselves, but then went on to consider carefully the extent to which other animals seem capable of performing the same activities. This procedure has different results from Descartes's doctrinal rejection of animal thinking: according to Locke, only abstraction (the operation most crucial in forming the ideas of mixed modes, on which morality depends) is utterly beyond the capacity of any animal. (Essay II xi 10)

Perception of ideas through the senses and retention of ideas in memory, Locke held, are passive powers of the mind, beyond our direct voluntary control and heavily dependent on the material conditions of the human body. The active powers of the mind include distinguishing, comparing, compounding, and abstracting. It is by employing these powers, Locke supposed, that we manufacture new, complex ideas from the simple elements provided by experience. The resulting complex ideas are of three sorts: (Essay II xii 4-7)

Modes are complex ideas that combine simpler elements to form a new whole that is assumed to be incapable of existing except as a part or feature of something else. The ideas of "three," "seventy-five," and even "infinity," for example, are all modes derived from the simple idea of "unity." We can understand these ideas and know their mathematical functions, whether or not there actually exist numbers of things to which they would apply in reality. "Mixed modes" similarly combine simple components without any presumption about their conformity to existing patterns, yielding all of our complex ideas of human actions and their value.

Substances are the complex ideas of real particular things that are supposed to exist on their own and to account for the unity and persistence of the features they exhibit. The ideas of "my only son," "the largest planet in the solar system," and "tulips," for example, are compounded from simpler ideas of sensation and reflection. Each is the idea of a thing (or kind of thing) that could really exist on its own. Since we don't understand all of the inner workings of natural objects, Locke supposed, our complex ideas of substances usually rely heavily on their secondary qualities and powers—the effects they are observed to have on ourselves and other things.

Relations are complex ideas of the ways in which other ideas may be connected with each other, in fact or in thought. The ideas of "younger," "stronger," and "cause and effect," for example, all involve some reference to the comparison of two or more other ideas.

Locke obviously could not analyze the content of every particular idea that any individual has ever had. But his defence of the empiricist principle did require him to show in principle that any complex idea can be derived from the simple ideas of sensation and reflection. The clarity, reality, adequacy, and truth of all of our ideas, Locke supposed, depend upon the success with which they fulfill their representative function. Here, we'll consider one of the most significant and difficult examples from each category:

Free Action

Among our modal ideas, Locke believed that those of mixed modes, which combine both sensory and reflective elements, are especially important, since they include the ideas of human actions and provide for their moral evaluation. Among the mixed modes, the ideas of power, volition, and liberty are the most crucial and difficult. To them Locke devoted a chapter (II xxi) that grew, with alterations in later editions, to become the longest in the Essay.

The idea of power is illustrated every time we do something. Whether we think or move, the feeling that our mental preference leads to action provides a simple instance of power. The exercise of that power is volition or will, and the action taken as a result is a voluntary one. Liberty or freedom, on Locke's view, is the power to act on our volition, whatever it may be, without any external compulsion or restraint. (Essay II xxi 7-12)

Under these definitions, the question of whether we have free will does not arise for Locke, since it involves what would later come to be called a category mistake. In particular, it does not matter whether we have control over our own preferences, whether we are free to will whatever we wish. (Essay II xxi 23-25) In fact, Locke offered a strictly hedonistic account of human motivation, according to which our preferences are invariably determined by the desire to seek pleasure and avoid pain. (Essay II vii 3) What does matter for freedom and moral responsibility is that we can act on our preferences, whatever their source, without any outside interference. If I could have done otherwise (given a different preference), then I act freely and am responsible for my action.

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