The Missing Shade of Blue

Last updated

"The Missing Shade of Blue" is an example introduced by the Scottish philosopher David Hume to show that it is at least conceivable that the mind can generate an idea without first being exposed to the relevant sensory experience. It is regarded as a problem by philosophers because it appears to stand in direct contradiction to what Hume had just written.

Contents

The source of the problem

In both A Treatise of Human Nature and An Enquiry Concerning Human Understanding , philosopher David Hume argues that all perceptions of the mind can be classed as either 'Impressions' or 'Ideas'. He further argues that:

We shall always find, that every idea which we examine is copied from a similar impression. Those who would assert, that this position is not universally true nor without exception, have only one, and at that an easy method of refuting it; by producing that idea, which, in their opinion, is not derived from this source. [1]

The Missing Shade of Blue Missing blue shade.svg
The Missing Shade of Blue

The problem of the missing shade of blue arises because just two paragraphs later Hume seems to provide just such an idea. He says:

There is, however, one contradictory phenomenon, which may prove, that it is not absolutely impossible for ideas to arise, independent of their correspondent impressions. I believe it will readily be allowed, that the several distinct ideas of colour, which enter by the eye, or those of sound, which are conveyed by the ear, are really different from each other; though, at the same time, resembling. Now if this be true of different colours, it must be no less so of the different shades of the same colour; and each shade produces a distinct idea, independent of the rest. For if this should be denied, it is possible, by the continual gradation of shades, to run a colour insensibly into what is most remote from it; and if you will not allow any of the means to be different, you cannot, without absurdity, deny the extremes to be the same. Suppose, therefore, a person to have enjoyed his sight for thirty years, and to have become perfectly acquainted with colours of all kinds, except one particular shade of blue, for instance, which it never has been his fortune to meet with. Let all the different shades of that colour, except that single one, be placed before him, descending gradually from the deepest to the lightest; it is plain, that he will perceive a blank, where that shade is wanting, and will be sensible, that there is a greater distance in that place between the contiguous colours than in any other. Now I ask, whether it be possible for him, from his own imagination, to supply this deficiency, and raise up to himself the idea of that particular shade, though it had never been conveyed to him by his senses? I believe there are few but will be of opinion that he can: And this may serve as a proof, that the simple ideas are not always, in every instance, derived from the correspondent impressions; though this instance is so singular, that it is scarcely worth our observing, and does not merit, that for it alone we should alter our general maxim. [1]

Responses to the problem

Some philosophers take Hume to task for presenting such a clear counter-example and then dismissing it as insignificant. Pritchard says:

This is, of course, just the kind of fact which should have led Hume to revise his whole theory. It is really effrontery on his part and not mere naiveness to ignore an instance so dead against a fundamental doctrine of his own...if he had considered the idea of cause as also to be ignored as being an isolated exceptional case, he would have had no reason to write the Treatise at all. [2]

Other philosophers take a more generous view of Hume's position. Jenkins says:

It is not so much that it is hardly worth altering a general thesis for one exception, which is very much the line Hume himself adopts. It is rather that the character of the phenomenon itself does not clearly run counter to the essential emphasis of Hume's doctrine. That emphasis really consists in the claim that, ultimately, there can be no ideas without impressions. His example does not, strictly, disobey this principle since, presumably, Hume would argue that, without sensory experience of other colours and particularly of other shades of blue, the missing shade could not be envisaged. It is not an admission of innatism, nor is it a claim that the idea was, as it were, produced out of a hat. It is perhaps nothing more than the concession that the natural powers of the mind are a little more enterprising than he had allowed for. [3]

It is sometimes said that the problem is even more severe than Hume thinks. Hume claims that this instance is 'singular', but Alexander Broadie writes:

The reason Hume's instance is not singular, is this: if indeed a person can have an idea of a shade of blue, though he had not had a previous impression of that shade, then we have to allow that a person could have an idea of missing shades of every other colour also; and there is no reason why we should restrict ourselves here to a consideration of only the visual one of the five sensory modalities. We could also have an idea of a missing sound, or taste, or smell, or tactile quality. [4]

However, as Williams points out, Hume's own words imply that he was fully aware of this. [5] Hume begins the relevant paragraph by talking about both sounds and colours. In addition, when first introducing the missing shade of blue he says, "except one particular shade of blue, for instance". The words "for instance" show that he could easily have chosen a different example. When he later says, "this instance is so singular, that it is scarcely worth our observing" he cannot be referring to this particular example, but rather to the type of exception that it represents.

When Hume says, "Let all the different shades of that colour, except that single one, be placed before him," he is assuming that colours are composed of a set of distinct independent hues, when in reality they form a continuum. However, Fogelin suggests, "Perhaps the reason that Hume does not see this is that he is thinking about the ideas of objects and not about objects themselves. In particular, he may hold that the notion of an indistinguishable difference between ideas make no sense. There is nothing more to an idea than that which can be discerned within it. If this is Hume's position, then the notion that two ideas can be different without being discernibly different would be a contradiction in terms." [6]

Suggested solutions

A fully adequate solution to the problem will have the following features.[ citation needed ] It will:

  1. Recognise that Hume believed the problem to be a genuine counter-example;
  2. Recognise that Hume included the example for a purpose;
  3. Provide an explanation that harmonizes well with other features of Hume's epistemology.

The problem has been tackled in various ways:

Mental mixing

Mental mixing is the solution proposed by Morris. [7] The idea here is that just as paints are mixed to produce the range of colour swatches found in a hardware store, so it should be possible for colours to be mixed in the mind in some kind of analogous way. However, without further argument it is not obvious that we are endowed with any such ability and, if we were, it is not clear why it would be limited to the mixing of closely related impressions; yet, if this were not the case, then, contrary to what Morris says, it would open the floodgates to a range of philosophically suspect ideas.

Colours as complex ideas

Another way of dissolving the problem has been to suggest that colours might also be regarded as complex ideas. This is tempting since Hume has only spoken of "the faculty of compounding, transposing, augmenting, or diminishing the materials afforded us by the senses." That 'augmenting' and 'diminishing' do not apply only to physical size is clear from the way Hume suggests that our idea of God "arises from reflecting on the operations of our own mind, and augmenting, without limit, those qualities of goodness and wisdom." However, this fails our third criterion, for Hume clearly distinguishes between complex ideas and simple ideas in a way that excludes the possibility of colours being complex. In the treatise (Book1, Part1, Section1), Hume writes:

Simple perceptions or impressions and ideas are such as admit of no distinction nor separation. The complex are the contrary to these, and may be distinguished into parts. Though a particular colour, taste, and smell, are qualities all united together in this apple, it is easy to perceive they are not the same, but are at least distinguishable from each other.

It does not undermine Hume's main concern

Hume's lack of concern might be explained by the fact that, although it contradicts the claim that all simple ideas are preceded by simple impressions, this is not a problem because it is not Hume's primary concern. This answer draws attention to what Hume says at the end of Section 2 of the Enquiries:

When we entertain, therefore, any suspicion that a philosophical term is employed without any meaning or idea (as is but too frequent), we need but enquire, from what impression is that supposed idea derived? And if it be impossible to assign any, this will serve to confirm our suspicion. By bringing ideas into so clear a light we may reasonably hope to remove all dispute, which may arise, concerning their nature and reality.

The fact that this contradicts Hume's explicitly stated purpose is explained by arguing that the Treatise has to be understood as a gradual unfolding of his views. The problem is that Hume never makes this clear, and if this is the way it is meant to be read then, as Williams says, "The narrative character of the Treatise is...disguised...by the superficial resemblance of the former to Locke's Essay... Also, there is the fact that he drops the problem in the same way in the Enquiry, which arguably lacks the narrative character of the Treatise ." [8]

The exception really is singular

Fogelin argues [9] that the reason this exception is a genuine exception that can be safely ignored is because despite being simple ideas, colours and shades can be organised into a highly organised colour space, (and that sounds and tastes, etc., can be similarly organised.) Hume allows that some simple ideas can be seen to be similar to one another without them sharing anything in common. The proviso that they do not share anything in common is important because otherwise this feature might be separated off and this would show that the original idea was in fact complex. In a note added to the Treatise commenting on abstract ideas Hume says:

It is evident, that even different simple ideas may have a similarity or resemblance to each other; nor is it necessary, that the point or circumstance of resemblance should be distinct or separable from that in which they differ. BLUE and GREEN are different simple ideas, but are more resembling than BLUE and SCARLET; though their perfect simplicity excludes all possibility of separation or distinction. It is the same case with particular sounds, and tastes and smells. These admit of infinite resemblances upon the general appearance and comparison, without having any common circumstance the same. And of this we may be certain, even from the very abstract terms SIMPLE IDEA. They comprehend all simple ideas under them. These resemble each other in their simplicity. And yet from their very nature, which excludes all composition, this circumstance, in which they resemble, is not distinguishable nor separable from the rest. It is the same case with all the degrees in any quality. They are all resembling and yet the quality, in any individual, is not distinct from the degree.

It is this very ability to recognize similarity that enables us to arrange the shades of blue in order and to notice that two adjoining shades differ more than any two other adjoining shades. If it be allowed that the notion of hue can arise through abstraction even though it cannot in any instance be separated from a given example, then it may be fairly argued that the ability to fill a gap in the colour space is quite a different matter to coming up with an isolated idea without any prior impression. It would certainly still be the case that the ability to conjure up the idea of the missing shade of blue is dependent on at least some prior impressions.

The problem with this claim is that there needs to be some way of showing that the exception really is limited and will not affect the important general claim that ideas depend on impressions. Suppose, therefore, a person to have enjoyed his sight for thirty years, and to have become perfectly acquainted with regular polygons of all kinds except the one having five sides...

Hume needs an exception

By whatever means the idea of the missing shade is to be created, there is still the question of why Hume takes such pains to present the example to his readers. Of course, it may just be that Hume was aware of it as an exception and was being open and honest. On the other hand, Nelson [10] suggests the intriguing possibility that far from being an oversight or an embarrassment to his wider project, the missing shade of blue example turns out to be crucial. Later Hume will divide all objects of human reason into 'Relations of Ideas' and 'Matters of Fact'. The former are certain and do not necessarily say anything about what actually exists in the world; the latter do make claims about the world, but "the contrary of every matter of fact is still possible". With this in mind it can be asked what status holds for the claim that "all our ideas or more feeble perceptions are copies of our impressions or more lively ones". If this is a Relation of Ideas, then it does not necessarily say anything true about the world, and this will not suit Hume's purpose at all; if it is a Matter of Fact, then the contrary must be possible. The inconsequential hypothetical possibility that we are able to raise up to ourselves the idea of the missing shade of blue, even if in practice this does not ever happen, will ensure that Hume's description of the origin of ideas is grounded in fact.

However, what is required of matters of fact is the logical possibility that they could be other than they are, not the practical possibility. This being the case, it is not necessary to construct an elaborately worked out example; it would be sufficient to say that we might have been constituted differently.

A singular exception doesn't really change the probability of Hume's thesis

Hume states that the model of rationality that humans use and must use [11] with regard to reasonings concerning matters of fact is not classical logic, but rather some kind of probabilistic logic where we associate a probability to factual statements (indeed, recalling Locke, Hume calls reasoning about matters of fact as merely probable, and contrasts it with the demonstrative kind of reasoning that instead concerns relations of ideas). [12] This is especially clear in Hume's treatment of miracles in Section X of the Enquiry , in which he claims that the probability of a certain factual thesis (in this case the thesis that "miracles do occur") is and must be evaluated by weighting all the evidences in favour of it with all the contrary evidences.

Since Hume's thesis that "all simple ideas come from simple impressions" is a matter of fact (ie. a factual statement), we can associate a probability to it. And the only way of evaluating the probability of this thesis is by weighting all the evidences. Since, except the "missing shade of blue", all the countless other direct evidences favour it, the influence (via Bayes theorem) of this singular contrary evidence on the probability of Hume's thesis can reasonably be expected to be minimal. And that's why Hume can reasonably say that this contrary evidence can be disregarded or, as he puts it, that «it is scarcely worth our observing, and does not merit, that for it alone we should alter our general maxim». [1]

Against such interpretation is the fact that Hume himself in Section II calls the "missing shade of blue" as a «proof, that the simple ideas are not always, in every instance, derived from the correspondent impressions», [1] where in Section VI he defines "proof" as not a demonstrative argument but as an argument from experience that «leaves no room for doubt or opposition». [12] If Hume is using his terminology consistently across sections, then his use of the term "proof" in reference to the "missing shade of blue" would imply that its effect on the probability of the thesis would not at all be minimal, but rather that it would enormously decrease it to the point of "leaving no room" in favour of the thesis itself.

See also

Related Research Articles

<i>An Enquiry Concerning Human Understanding</i> 1748 book by David Hume

An Enquiry Concerning Human Understanding is a book by the Scottish empiricist philosopher David Hume, published in English in 1748. It was a revision of an earlier effort, Hume's A Treatise of Human Nature, published anonymously in London in 1739–40. Hume was disappointed with the reception of the Treatise, which "fell dead-born from the press," as he put it, and so tried again to disseminate his more developed ideas to the public by writing a shorter and more polemical work.

<span class="mw-page-title-main">David Hume</span> Scottish philosopher, historian, economist and essayist (1711–1776)

David Hume was a Scottish philosopher, historian, economist, and essayist who was best known for his highly influential system of empiricism, philosophical skepticism and metaphysical naturalism. Beginning with A Treatise of Human Nature (1739–40), Hume strove to create a naturalistic science of man that examined the psychological basis of human nature. Hume followed John Locke in rejecting the existence of innate ideas, concluding that all human knowledge derives solely from experience. This places him with Francis Bacon, Thomas Hobbes, John Locke, and George Berkeley as an empiricist.

<span class="mw-page-title-main">Empiricism</span> Idea that knowledge comes only/mainly from sensory experience

In philosophy, empiricism is an epistemological view which holds that true knowledge or justification comes only or primarily from sensory experience and empirical evidence. It is one of several competing views within epistemology, along with rationalism and skepticism. Empiricists argue that empiricism is a more reliable method of finding the truth than purely using logical reasoning, because humans have cognitive biases and limitations which lead to errors of judgement. Empiricism emphasizes the central role of empirical evidence in the formation of ideas, rather than innate ideas or traditions. Empiricists may argue that traditions arise due to relations of previous sensory experiences.

<span class="mw-page-title-main">George Berkeley</span> Anglo-Irish philosopher and bishop (1685–1753)

George Berkeley – known as Bishop Berkeley – was an Anglo-Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism". This theory denies the existence of material substance and instead contends that familiar objects like tables and chairs are ideas perceived by the mind and, as a result, cannot exist without being perceived. Berkeley is also known for his critique of abstraction, an important premise in his argument for immaterialism.

<span class="mw-page-title-main">Primary color</span> Fundamental color in color mixing

A set of primary colors or primary colours consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printing, and paintings. Perceptions associated with a given combination of primary colors can be predicted by an appropriate mixing model that reflects the physics of how light interacts with physical media, and ultimately the retina. The most common color mixing models are the additive primary colors and the subtractive primary colors. Red, yellow and blue are also commonly taught as primary colours, despite some criticism due to its lack of scientific basis.

<span class="mw-page-title-main">Idea</span> Mental image or concept

In common usage and in philosophy, ideas are the results of thought. Also in philosophy, ideas can also be mental representational images of some object. Many philosophers have considered ideas to be a fundamental ontological category of being. The capacity to create and understand the meaning of ideas is considered to be an essential and defining feature of human beings.

<span class="mw-page-title-main">Problem of induction</span> Question of whether inductive reasoning leads to definitive knowledge

The problem of induction is a philosophical problem that questions the rationality of predictions about unobserved things based on previous observations. These inferences from the observed to the unobserved are known as "inductive inferences". David Hume, who first formulated the problem in 1739, argued that there is no non-circular way to justify inductive inferences, while acknowledging that everyone does and must make such inferences.

<span class="mw-page-title-main">Is–ought problem</span> Philosophical problem articulated by David Hume

The is–ought problem, as articulated by the Scottish philosopher and historian David Hume, arises when one makes claims about what ought to be that are based solely on statements about what is. Hume found that there seems to be a significant difference between positive statements and prescriptive or normative statements, and that it is not obvious how one can coherently transition from descriptive statements to prescriptive ones. Hume's law or Hume's guillotine is the thesis that an ethical or judgmental conclusion cannot be inferred from purely descriptive factual statements.

<span class="mw-page-title-main">Hume's fork</span> English philosophy

Hume's fork, in epistemology, is a tenet elaborating upon British empiricist philosopher David Hume's emphatic, 1730s division between "relations of ideas" and "matters of fact." As phrased in Immanuel Kant's 1780s characterization of Hume's thesis, and furthered in the 1930s by the logical empiricists, Hume's fork asserts that all statements are exclusively either "analytic a priori" or "synthetic a posteriori," which, respectively, are universally true by mere definition or, however apparently probable, are unknowable without exact experience.

Inductive reasoning is any of various methods of reasoning in which broad generalizations or principles are derived from a body of observations. This article is concerned with the inductive reasoning other than deductive reasoning, where the conclusion of a deductive argument is certain given the premises are correct; in contrast, the truth of the conclusion of an inductive argument is at best probable, based upon the evidence given.

Bertrand Russell makes a distinction between two different kinds of knowledge: knowledge by acquaintance and knowledge by description. Whereas knowledge by description is something like ordinary propositional knowledge, knowledge by acquaintance is familiarity with a person, place, or thing, typically obtained through perceptual experience. According to Bertrand Russell's classic account of acquaintance knowledge, acquaintance is a direct causal interaction between a person and some object that the person is perceiving.

The new riddle of induction was presented by Nelson Goodman in Fact, Fiction, and Forecast as a successor to Hume's original problem. It presents the logical predicates grue and bleen which are unusual due to their time-dependence. Many have tried to solve the new riddle on those terms, but Hilary Putnam and others have argued such time-dependency depends on the language adopted, and in some languages it is equally true for natural-sounding predicates such as "green". For Goodman they illustrate the problem of projectible predicates and ultimately, which empirical generalizations are law-like and which are not. Goodman's construction and use of grue and bleen illustrates how philosophers use simple examples in conceptual analysis.

Association of ideas, or mental association, is a process by which representations arise in consciousness, and also for a principle put forward by an important historical school of thinkers to account generally for the succession of mental phenomena. The term is now used mostly in the history of philosophy and of psychology. One idea was thought to follow another in consciousness if it were associated by some principle. The three commonly asserted principles of association were similarity, contiguity, and contrast, numerous others had been added by the nineteenth century. By the end of the nineteenth century physiological psychology was so altering the approach to this subject that much of the older associationist theory was rejected.

<i>A Treatise of Human Nature</i> Work by David Hume

A Treatise of Human Nature: Being an Attempt to Introduce the Experimental Method of Reasoning into Moral Subjects (1739–40) is a book by Scottish philosopher David Hume, considered by many to be Hume's most important work and one of the most influential works in the history of philosophy. The Treatise is a classic statement of philosophical empiricism, scepticism, and naturalism. In the introduction Hume presents the idea of placing all science and philosophy on a novel foundation: namely, an empirical investigation into human nature. Impressed by Isaac Newton's achievements in the physical sciences, Hume sought to introduce the same experimental method of reasoning into the study of human psychology, with the aim of discovering the "extent and force of human understanding". Against the philosophical rationalists, Hume argues that the passions, rather than reason, cause human behaviour. He introduces the famous problem of induction, arguing that inductive reasoning and our beliefs regarding cause and effect cannot be justified by reason; instead, our faith in induction and causation is caused by mental habit and custom. Hume defends a sentimentalist account of morality, arguing that ethics is based on sentiment and the passions rather than reason, and famously declaring that "reason is, and ought only to be the slave to the passions". Hume also offers a sceptical theory of personal identity and a compatibilist account of free will.

<span class="mw-page-title-main">Primary–secondary quality distinction</span> Epistemological and metaphysical dualism in modern philosophy

The primary–secondary quality distinction is a conceptual distinction in epistemology and metaphysics, concerning the nature of reality. It is most explicitly articulated by John Locke in his Essay concerning Human Understanding, but earlier thinkers such as Galileo and Descartes made similar distinctions.

"Of Miracles" is the tenth section of David Hume's An Enquiry Concerning Human Understanding (1748). In this piece, Hume states that evidence of miracles is never sufficient for rational belief.

An Enquiry Concerning the Principles of Morals (EPM) is a book by Scottish enlightenment philosopher David Hume. In it, Hume argues that the foundations of morals lie with sentiment, not reason.

Moral sense theory is a theory in moral epistemology and meta-ethics concerning the discovery of moral truths. Moral sense theory typically holds that distinctions between morality and immorality are discovered by emotional responses to experience. Some take it to be primarily a view about the nature of moral facts or moral beliefs —this form of the view more often goes by the name "sentimentalism". Others take the view to be primarily about the nature of justifying moral beliefs —this form of the view more often goes by the name "moral sense theory". However, some theorists take the view to be one which claims that both moral facts and how one comes to be justified in believing them are necessarily bound up with human emotions.

The philosophy of self examines the idea of the self at a conceptual level. Many different ideas on what constitutes self have been proposed, including the self being an activity, the self being independent of the senses, the bundle theory of the self, the self as a narrative center of gravity, and the self as a linguistic or social construct rather than a physical entity. The self is also an important concept in Eastern philosophy, including Buddhist philosophy.

In philosophy, constant conjunction is a relationship between two events, where one event is invariably followed by the other: if the occurrence of A is always followed by B, A and B are said to be constantly conjoined. A critical philosophical question concerns the relationship between constant conjunction and causation, which has implications in the philosophy of science.

References

  1. 1 2 3 4 Enquiries , Section II. Of the Origin of Ideas
  2. ↑ Pritchard, H.A. (1950) Knowledge and Perception, Oxford: Clarendon Press, page 177
  3. ↑ Jenkins, J. J., (1992) Understanding Hume, Edinburgh University Press, page 22
  4. ↑ Broadie, A. (1990) The Tradition of Scottish Philosophy: A New Perspective on the Enlightenment, Polygon, page 97
  5. ↑ Williams, W.H. 'Is Hume's Shade of Blue a Red Herring?', Synthese 92, page 86
  6. ↑ Fogelin, R.J., (1992) Philosophical Interpretations, Oxford University Press, page 75
  7. ↑ William Edward Morris (http://plato.stanford.edu/entries/hume/)
  8. ↑ Williams, W.H. page 96
  9. ↑ Fogelin, R.J., (1992) Philosophical Interpretations, Oxford University Press, page 75
  10. ↑ Nelson, J.O. "Hume's Missing Shade of Blue Re-viewed", Hume Studies Volume XV Number 2(November 1989) 353-364.
  11. ↑ Hume intends this model of rationality to be not only explanatory of how we do reason, but also normative by prescribing how we should reason.
  12. 1 2 Hume writes in Section VI (On Probability) of the Enquiry : «Mr. Locke divides all arguments into demonstrative and probable. In this view, we must say, that it is only probable that all men must die, or that the sun will rise tomorrow. But to conform our language more to common use, we ought to divide arguments into demonstrations, proofs, and probabilities. By proofs meaning such arguments from experience as leave no room for doubt or opposition».
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.