An Enquiry Concerning Human Understanding | Study Guide

David Hume

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An Enquiry Concerning Human Understanding | Section 2 : Of the Origin of Ideas | Summary



Hume asserts that there are two types of perceptions, or mental events: impressions and ideas. Outer perceptions are those experiences occasioned by organs of sense: visual, tactile, auditory, olfactory, and gustatory. Inner impressions, perceptions, or reflections are those mental experiences associated with emotions.

Ideas are "copies" of impressions. Even when ideas occur apparently simultaneously with an impression, they are still derived from them. Impressions are the original mental items of experience, such as this color or that sound; ideas store those impressions. Hence, "The most lively thought is still inferior to the dullest sensation."

That storehouse of ideas allows the mind to remember, to imagine, and to think about and reflect upon. The mind is also restricted to that storehouse. Absent an impression, the mind does not have an idea on which to operate. The imagination can dismantle and compound ideas to create new ones, but it cannot create entirely new ideas that cannot be traced to an original impression.

Not every idea is derived directly from experience. Some ideas arise in dreams, some are inaccurate memories, and still others from arise from training or indoctrination. Hume says, "When we think of a golden mountain, we only join two consistent ideas, gold and mountain, with which we were formerly acquainted." Similarly, one can conceive of a "virtuous horse," since "from our own feeling, we can conceive virtue."

Hume offers two arguments to support this view. First, an analysis of any idea can be resolved "into such simple ideas as were copied from a precedent feeling or sentiment." Any proposal that there are ideas not generated in this way—that is, any proposal that there are real ideas whose source is independent of experience—must be accompanied by the presentation of an instance. Second, the absence of an organ of sense will correlate to the absence of corresponding ideas: "A blind man can form no notion of colors; a deaf man of sounds." Alternatively, the absence of the occasion for an idea will also correlate to the absence of the idea. One who has not tasted wine, for example, will have no idea of its "relish."

No sooner does Hume make this challenge than he offers a response. "There is ... one contradictory phenomenon, which may prove, that it is not absolutely impossible for ideas to arise, independent of the correspondent impressions." Though color ideas are distinct from each other, as are auditory ideas, they are nevertheless similar. Hume infers, given that this is true, the same can be said for specific shades of a color. Suppose a man who has never seen a particular shade of blue were presented with the contiguous gradations of shades of blue, as would be found along a color strip. The only shade missing would be that shade of blue he has never seen. Hume concludes that he would see a blank where that shade of blue should be. It is possible, however, that he could, "from his own imagination," supply that missing shade, "though it had never been conveyed to him by his senses." This example does not, Hume thinks, undermine his thesis.

Hume concludes the section by reiterating his view that any legitimate idea is one that can be traced back to an original impression. He concludes that the language used to articulate ideas should, accordingly, be restricted. Following this proposal, he thinks, could "banish all that jargon, which has so long taken possession of metaphysical reasonings." In particular, abstract ideas, such as substance, "are naturally faint and obscure" and so allow the mind only the most tenuous of grasps and are, therefore, particularly pernicious in presenting the illusion of legitimacy. Consequently, when a word is used in philosophy that strikes one as suspicious, that is, as having no real meaning, one should seek the impression from which it is supposedly derived.


Hume follows the British empiricist tradition shared by his countrymen, the Englishman John Locke and the Irishman George Berkeley. All agree that knowledge is derived from experience. Where, however, both Locke and Berkeley draw conclusions about entities such as God, the self, and freedom from this empirical starting point, Hume does not. He does begin in much the same way by discussing perceptions in terms of sensory experiences and ideas. However, he relentlessly follows that starting point to some startling—and skeptical—conclusions.

Hume's philosophy of mind follows the initial sense impression, be it internal or external, to its copies. At times it seems as if impressions and ideas are indistinguishable, but Hume provides a standard by which to mark their separation: vividness or liveliness. Later he provides another criterion: meaning. This evaluative criterion allows one to separate legitimate from illegitimate ideas, with only the former connected to an original impression. So, while there are not any existent virtuous horses or golden mountains—they are mere fictions—the constituents of these compound ideas are legitimate simple ideas. Consequently, meaningful language is one that enlists meaningful, that is, empirically verifiable, terms. Any talk about God, for example, can be evaluated according to the criterion of meaningfulness.

Hume also distinguishes the faculties of imagination and memory, important as they are to the production of ideas. Following previous thinkers, Hume considers imagination as a picturing faculty. One can generate a mental picture of an object and attach it to another picture to create a new one, like Pegasus. Hume extends this faculty, however, to include items that cannot be explicitly pictured, such as the virtuous horse. Insofar as this idea is a creation, however, it is the product of the imagination, which often works in concert with memory, as when one's imagining of that virtuous horse involves calling to mind the image of a horse one saw previously.

In this section, Hume also challenges his foundational view that there are no ideas without a corresponding original impression. This is the case of the missing shade of blue. It is possible for a man who has never seen a particular shade of blue to manufacture it in the context of a color strip consisting of all the other shades in gradation. A number of scholars think, in so positing this possibility, Hume has opened the door to the criticism of his view that all ideas are derived from impressions. One response, on Hume's behalf, is that there is an impression of the shade of blue in question, even if this particular individual has not experienced it. Consequently, the idea itself is meaningful. This response seems to skirt part of the issue, however. The question has less to do with the possibility of experiencing the shade of blue than with being able to supply it absent the experience. Perhaps a sort of middle ground is that the man could manufacture the idea on the basis of the two shades adjoining it, with the foreknowledge that such a shade could be found in experience.

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