I was reading An Enquiry concerning Human Understanding by David Hume, and came across (a couple days ago) a part wherein Hume draws a counterexample towards his epistemological theory and drops it. The paragraph in question is as follows

"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."

I was quite troubled by how Hume dismissed the example as inconsequential, considering that the event could further imply missing auditory or other sensory qualities which could be conceived without a corresponding impression. What then, is this counterexample dismissed?

My idea was that perhaps the ideas derived from the impressions of the nearby colors could be combined, augmented and diminished (three of the four ways Hume states that ideas can be conjoined) to create the idea of the missing shade. Hence, perhaps the idea of the missing shade, rather than being a simple idea, would be a complex idea with no corresponding impression. But if this is the case, why then does Hume claim that the example is a counterexample? I myself am highly skeptical of my idea, so if there exists a better defense from a more experienced Hume scholar, it would be greatly appreciated.

  • Hello. There is a good Wikipedia entry on this topic. You can find there several suggested solutions to the blue shade riddle (including the solution that occurred to you) and an assessment of each. Commented Apr 15, 2015 at 19:56
  • Also, see my answer there for the answer to the question.
    – user5172
    Commented Aug 7, 2015 at 15:52
  • I haven't read the two questions super carefully but if someone thinks they are significantly non-duplicating, please tell and I'll undo the relating.
    – virmaior
    Commented Aug 9, 2015 at 8:47

1 Answer 1


Hume isn't dismissing the example, as such; it raises a question of importance in his philosophy: the relation between the idea of an impression and the impression itself.

Here, this would be the idea of the colour blue, and the colour blue itself.

ie there is a blue cup; it is blue; I have in my mind the idea of blueness.

He's dismissing the thought-experiment, or illustration, as something that can hardly arise in practise. It's in this sense that the example is inconsequential.

I asked a similar question phrased in a different way on this, and for different reasons; and by some stroke of strange serendipitous fortune I chose the same colour as he did.

  • In brief: the counterexample hasn't ever been raised in practice, so isn't very significant -- am i right? Thanks, @Mozibur Ullah
    – Ron
    Commented Apr 15, 2015 at 1:58
  • Are there any sources from Hume scholars relating to this paragraph?
    – Ron
    Commented Apr 15, 2015 at 2:04
  • Also, is this dealt with in more detail in A Treatise On Human Nature by Hume, published earlier (I haven't read this longer work of Hume).
    – Ron
    Commented Apr 15, 2015 at 2:05
  • Not quite; it's more like 'imagine a blue elephant' because we want to discuss what we mean by blueness; and then after finishing the discussion, we dismiss the blue elephant; we no longer want to think about it - because there aren't any blue elephants. Commented Apr 15, 2015 at 2:06
  • I'm sure that there are; but unfortunately I don't know any. Commented Apr 15, 2015 at 2:08

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