Entry in The Encyclopedia of Empiricism, (Greenwood Press, 1997) Don Garrett and Ed Barbanell, eds. Copyright 1997

Saul Traiger, Occidental College

IDEAS. LOCKE used the term "to stand for whatsoever is the Object of the Understanding when a Man thinks." (Essay, Ii8) Although theorizing about ideas figures prominently in philosophy before him, Locke introduced what became known as the "New Way of Ideas," by considering all metaphysical and epistemological questions through an examination of the nature and origin of the mind's content. Although sometimes disagreeing with him on important details, other empiricists of the modern era follow Locke by first theorizing about the origin of ideas, and second by classifying ideas into types, based on origin and characteristics discovered by mental inspection. The shared features of the empiricist notion of ideas is that ideas are not innate, and that they are the result of sensation and reflection. (See INNATENESS)

In contrast to Plato, for whom ideas were archetypes abstracted from experience and obscured by it, for the empiricist, ideas are first and foremost particular mental contents founded on experience; ABSTRACT IDEAS are not given in experience but derive from mental operations involving particular ideas which are so given. The origins of this conception of ideas can be traced to Sextus EMPIRICUS and the ancient skeptics. Empiricus distinguished between the apprehensive nature of sense perception, which furnishes us with appearances, and the intellect, by means of which we attempt to judge truth and falsity. When we try to judge, for example, whether external objects have the properties we sense them as having, we find that the senses can contradict themselves. For Empiricus, we ought not doubt the appearances, but rather "the account given of the appearances." (Outlines of Pyrrhonism, p. 15) Here we find an early skeptical answer to the question of the relation between ideas and external objects. Empiricus also allowed that we can apprehend the intellect itself, thus anticipating the modern notion of ideas of reflection.

Rene Descartes, (1596-1650) although not an empiricist, did much to introduce theorizing about ideas. Descartes initially defines ideas as belong to a subclass of the class of thoughts, those which are "images of things." The examples of ideas he gives are the thought of "a man, or a chimera, or the sky, or an angel, or God." (Philosophical Writings, Vol II, p. 25) Emotions, volitions, and judgements are not mere ideas. They include ideas as their content, but also contain an additional attitude or stance.

Like Sextus Empiricus, Descartes holds that ideas by themselves cannot introduce falsehood or error. Ideas are modifications of the mind, properties of the mental SUBSTANCE which are revealed through clear and distinct perception. Unlike Empiricus, however, Descartes does not hold that all ideas originate in sense perception. His tripartite classification of ideas in the Meditations on First Philosophy is based on their origin: Ideas are innate, adventitious or made up. Only adventitious ideas are acquired through sense perception. Descartes grants that our ideas appear to come from sense perception, but he argues that such a view is the result not of "reliable judgement" but rather a "blind impulse." Our most important ideas, including the idea of God and the idea of oneself as a thinking thing, are innate.

Descartes' philosophy forms the backdrop for the theories of ideas of his followers, the Cartesians, and their critics. GASSENDI, an early modern empiricist, took issue with Descartes's tripartite classification. In the Objections and Replies to Descartes' Meditations, Gassendi argued that all ideas are adventitious; ideas of the imagination, "made up" ideas, are simply concatenations of sensory ideas. Descartes responded that only ideas which are images are derived from the senses. The ideas of a chiliagon, Descartes had argued in Meditation VI, is perfectly intelligible, though not imaginable as a construct of sensory perceptions. It is an idea of the intellect.

Controversy arose over the extent to which the mind could author its ideas. Descartes himself had argued that some ideas are the result of external objects impinging on our senses, for if that were not the case, God would be a deceiver. Following Descartes, Arnauld held that some ideas are authored by the mind, e.g. the ideas of existence and thought. Other ideas come from the senses and are signs of the objects they represent. One difficulty with the Cartesian view is that sensory ideas, though mental, are caused by physical things, external objects. Although our knowledge that our ideas are so caused depends on our knowledge that God is no deceiver, it is still the case that a mental phenomenon, an idea, is brought about by entirely different substance, matter.

Malebranche, another Cartesian, sought to resolve the ontological mismatch between ideas and their causes with the doctrine that we see all things in God. We don't perceive external objects, such as the sun and the stars. To do so, Malebranche argued, our souls would have to leave our bodies and "stroll about the heavens." (The Search After Truth, III,ii,1) What we perceive are our ideas, which are the mind's immediate objects, the "object closest to the mind, when it perceives something." Further, we don't author any of our ideas, even in response to the "impressions that objects make on the body." (Search, III,ii,3). The claim of human authorship gives us powers which God doesn't have, since it means that we can create ideas which were not already created by God. Malebranche concludes that all our ideas are those works of God which are revealed to us.

The philosophical treatment of ideas did not, then, begin with Locke. On the contrary, Locke, as well as Berkeley and Hume, attempts to explain human understanding in terms of ideas, fully aware of the controversies raging about their origin and ontological status. Malebranche had argued that ideas are spiritual items, not material items, and our having ideas is a matter of the uniting of our souls with God's soul. Locke takes this account of the having of ideas to be more problematic than his own, in which sensory ideas are the effects of external objects. For Locke, Malebranche's "intimate union" of our minds with God's "signifies literally nothing." (Opinion, p. 223) Locke has another difficulty with Malebranche's account. Malebranche distinguishes sensations from the ideas of the intellect, but vacillates on whether sensations are ideas or physical states accounted for in terms of human physiology. Yet this leads to the same problem Malebranche's doctrine of seeing everything in God was supposed to avoid: If sensations are physical, then how can we see all things in God when we perceive the scent of a rose? If sensations are not physical, how can he distinguish the ideas of the intellect from the sentiments?

Locke's own theory of ideas attempts to avoid these difficulties by using the term "idea" in a broad sense to cover anything about which one thinks, and by taking "thinks" to include both sensation and reflection. Accordingly, for Locke, there are two types of ideas, ideas of sensation and ideas of reflection. Examples of the former are "Yellow, White, Heat, Cold, Soft, Hard, Bitter, Sweet, and all those which we call sensible qualities." (Essay, II,i,3) The source of ideas of sensation are external objects. Reflection, "The other Fountain" of ideas, supplies us with ideas such as "Perception, Thinking, Doubting, Believing, Reasoning, Knowing, Willing," that is, ideas of the mind's own operations. The source of ideas of reflection is the mind itself, not external objects. Yet Locke insists that this source is also a matter of experience. Our first ideas must be ideas of sensation, since the mind can't reflect on its operations until there are some operations to reflect on. Introspection reveals that sensation and reflection are the only sources of ideas; therefore all ideas are either simple ideas of sensation or reflection, or complex ideas concatenated from simple ideas. (See SIMPLE/COMPLEX)

External objects have the power to bring about ideas in us, but the ideas themselves are not in the external objects, only the power to produce ideas, which Locke calls "qualities," are in the objects. The qualities in external objects produce ideas in us by the motion of matter in those objects, which motion brings about further motions in our bodies. Locke calls these "primary qualities." These qualities produce ideas which resemble qualities which the objects really have. Other ideas, of "secondary qualities," such as heat and light, do not resemble actual properties of the objects. The same object can feel hot to one hand and cold to another. Locke explains that this happens because the ideas of secondary qualities arise from the combination of the motions in the object and the motions of the affected part of the body. (See PRIMARY/SECONDARY QUALITIES) Fully aware of Malebranche's worry about how matter can cause ideas, Locke sees no difficulty in an explaining ideas of sensation in terms of such interaction. "It being no more impossible, to conceive, that God should annex such Ideas to such Motions, with which they have no similitude; than that he should annex the Idea of Pain to the motion of a piece of Steel dividing our Flesh, with which that Idea hath no resemblance." (Essay, II,viii,13)

Locke's insistence that an account of the nature and origin of ideas provides the starting point for any theory of human understanding was novel enough that Locke offers a pre-emptive defense of his widespread use of the term "idea" in the Introduction to the Essay. (Essay I,i,8) Some readers found Locke's wide use of the term radical and puzzling. Lee and Sergeant interpreted Locke's emphasis on ideas as a commitment to idealism. Others, such as Stillingfleet and Toland, argued that Locke's use of the term "ideas" deviated from common usage. Others, however, found that Locke provided a framework for understanding how experience brings about the entire range of mental phenomena, and the appeal to ideas gained widespread acceptance in modern British philosophy.

BERKELEY, like Locke, took the objects of human understanding to be ideas. He also follows Locke in recognizing ideas of sense, reflection, and ideas formed from these two sources. Ideas are either "imprinted on the senses, or else such as are perceived by attending to the passions and operations of the mind, or lastly, ideas formed by help of memory and imagination, either compounding, dividing, or barely representing those originally perceived in the aforesaid ways." (Principles, Part I, Sec. 1) Ideas are had by the mind and depend on the mind for their existence. This view of the dependence of ideas on the mind is close to Descartes' view that ideas are accidents of the soul as substance. It is a consequence of this dependence that, as Berkeley famously puts it, "the existence of an idea consists in its being perceived." (Principles, Part I, Section II)

Whereas Locke understood ideas of sense to represent external objects, the final objects of sense for Berkeley are the ideas themselves. Berkeley's insistence that the only things we perceive are our ideas leads him to the conclusion that we don't perceive external objects at all, even through the mediation of ideas. To perceive such external objects would mean either that we perceive non-ideas, or that things we perceive, external objects, as non-ideas, exist unperceived. Either way we have a contradiction. Berkeley's conception of ideas as the sole objects of perception is clearly at work in his rejection of the existence of an external world. Berkeley took his system to avoid the SKEPTICISM engendered by a theory such as Locke's where ideas represent external objects, but where one can't show that the objects represented exist as represented.

If ideas are not caused by external objects, how can Berkeley account for the fact that ideas come to us against our will, and that the interconnections we perceive appear not to be our own cognitive inventions? Here Berkeley resurrects a version of Malebranche's theory that we see all things in God. The order we perceive in the having of ideas, as well as their independence of our will, is proof of God's existence. God, as omniscient perceiver, has created all the ideas there are through divine perception. Human perception is access to God's mind. God provides ideas directly. There's no need for external objects to mediate our insight into God's ideas.

David HUME thought that the generality of Locke's theory of ideas threatened one of its central claims, the claim that there are no innate ideas. Some of the items Locke takes to be ideas, namely the passions, are, on Hume's view, perceptions which arise "immediately from nature." (Abstract, p. 10) If they are ideas, they are innate. At the same time Hume criticizes Malebranche's narrow conception of ideas for failing to account for the role of sensation in the origin of ideas. Hume reconciles the narrow and the wide theories of ideas by dividing perceptions into two classes, impressions and ideas. Impressions include "all our sensations, passions, and emotions, as they make their first appearance in the soul." (Treatise of Human Nature, I,i,1) Ideas are the "faint images" of impressions. We have ideas when we think or remember. Impressions are original; ideas are copies of impressions, and distinguished from them phenomenologically by having less force and vivacity.

The distinction between sensation and reflection is maintained by Hume, though unlike Locke, Hume does not distinguish ideas of sensation and reflection, but only impressions of sensation and reflection. All simple ideas derive from simple impressions. It is a basic principle of Hume's philosophy "That all our simple ideas in their first appearance, are derived from simple impressions, which are correspondent to them, and which they exactly represent." (Treatise, I,i,1) Ideas can, in turn, bring about impressions. An impression of desire may result from the idea of pleasure. The idea of pleasure, however, must itself derive from an antecedent impression of pleasure. About the origin of our impressions themselves Hume has little to say. He appears to think that determining the origins of impressions is outside of the bounds of philosophical inquiry. Some commentators take Hume to hold that impressions of sensation are caused by external objects, as Locke held ideas of sense are caused. However, in the Treatise Hume criticizes this view, which he calls the doctrine of double existence, as an obscure philosophical invention which derives simultaneously from our vulgar or ordinary conception and the philosopher's rejection of that very conception.

The principle that all simple ideas derive from simple impressions is put to use in Hume's examination of rival philosophical systems. It plays an important role in Hume's rejection of rationalist accounts of CAUSATION and SUBSTANCE, in addition to the more obvious employment in arguments against innate ideas. Hume rejects the claim that we have simple ideas of causation and substance by showing that there are no corresponding antecedent simple impressions. Hume's treatment of ideas, like Berkeley's and Locke's, emphasizes both the limitations of the mind -- the only ideas we can have are those which arise from sensation and reflection, and the mind's great imaginative power to go beyond what's given in sensation and reflection by the ASSOCIATION and concatenation of ideas.

LOGICAL POSITIVISM and LOGICAL EMPIRICISM each acknowledge their debt to the empiricist account of ideas. A.J. Ayer interprets Berkeley's use of the term "idea" to mean sense content or sense data, and takes sense content to be metaphysically neutral, neither mental nor physical, but rather the basis on which the mental and physical must be defined. Ayer, CARNAP and REICHENBACH, among others, saw in the theory of ideas the germ of their verification principle of meaning, which holds that the only terms which are meaningful are those which can be empirically verified, that is, defined in terms of sense contents. While acknowledging that the twentieth century positivists and empiricists took themselves to be advancing the views of Locke, Berkeley and Hume with the tools of the modern physics and logic, many commentators hold that Ayer and others oversimplified and misunderstood range of views understood as the theory of ideas.

Post-positivist critiques of foundationalism and PHENOMENALISM find fault with any theory of ideas which attempts to treat ideas both as sensations and as thoughts. Wilfrid Sellars argues that Locke, Berkeley and Hume each took our ability to have and recognize determinate ideas or impressions, such as an idea of a particular instance of the color red, to be given and unproblematic, and they explained our ability to form abstract ideas in terms of it. But what are the criteria for the correct identification of a particular idea as the idea of this particular shade of red? Sellars argues that our ability to master the logic of sensations, for sensations to play a role in our thought, presupposes the mastery of higher level concepts, including the concept of external objects.

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