The Missing Shade of Blue: Difference between revisions

"'''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 perception|sensory]] experience. It is regarded as a problem by philosophers because it appears to stand in direct contradiction to what Hume had justpreviously written.

{{quoteblockquote|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.<ref>''[[An Enquiry Concerning Human Understanding|Enquiries]]'', Section II. Of the Origin of Ideas<name="Section2"/ref>}}

{{quoteblockquote|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.<ref name="Section2">''[[An Enquiry Concerning Human Understanding|Enquiries]]'', Section II. Of the Origin of Ideas</ref>}}

{{quoteblockquote|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.<ref>[[Harold Arthur Prichard|Pritchard, H.A.]] (1950) Knowledge and Perception, Oxford: Clarendon Press, page 177</ref>}}

{{quoteblockquote|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.<ref>Jenkins, J,. J., (1992) Understanding Hume, Edinburgh University Press, page 22</ref>}}

{{quoteblockquote|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.<ref>Broadie, A. (1990) The Tradition of Scottish Philosophy: A New Perspective on the Enlightenment, Polygon, page 97</ref>}}

It is also said{{By whom|date=September 2013}} that whenWhen Hume says, "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", he is assuming that colours are composed of a set of distinct independent hues, when in reality they form a [[Continuum (measurement)|continuum]]. In this matter it does seem as though Hume is simply wrong. 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."<ref>Fogelin, R.J., (1992) Philosophical Interpretations, Oxford University Press, page 75</ref>

{{quoteblockquote|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 doesn'tdoes not undermine Hume's main concern===

{{quoteblockquote|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.}}

In other words, Hume's concern is that his principle can be used as a "critical tool for clearing discourse of metaphysical disputes, and not necessarily that it provides an exact account of the origin of our ideas."{{Who|date=September 2013}} 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 [[John Locke|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 ''[[A Treatise of Human Nature|Treatise]]''."<ref>Williams, W.H. page 96</ref>

{{quoteblockquote|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 beis 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 tofrom 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.

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<ref>Nelson, J.O. "Hume's Missing Shade of Blue Re-viewed", Hume Studies Volume XV Number 2(November 1989) 353-364.</ref> 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 '[[Relation of Ideas|Relations of Ideas]]' and '[[wikt:matter of fact|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 doesn'tdoes not ever happen, will ensure that Hume's description of the origin of ideas is grounded in fact.