The Missing Shade of Blue - Responses To The Problem

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.”

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."

In their own ways both these views fail to address the problem of the missing shade of blue. The first fails to offer an explanation as to why Hume has presented us with the contradiction and the latter fails to deal with the fact that Hume is himself insistent that it really is a contradiction.

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.”

However, as Williams points out, Hume’s own words imply that he was fully aware of this. 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.

It is also said that when 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. In this matter it does seem as if 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."