It was the title that made me pick up this book off the shelf in the library. The Missing Shade of Blue refers to David Hume’s thesis, or rather objection to his thesis, that simple ideas are derived from corresponding simple impressions. But Hume also argues that under certain conditions it seems possible that an idea can emerge without being caused by an impession.  We can imagine a purple horse without having seen one. As he describes in the ‘missing shade of blue’ thought experiment

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.*

Jennie Erdal’s book , “The Missing Shade of Blue. A philosophical mystery”   refers to our ability to make sense of something that we have not experienced. Happiness, perhaps!

It is a book about the dangers and the delights of philosophy which as Carrie (one of the characters in the story) warns, it can “seriously damage your heart”. It is about love and death “the principal concerns in most people’s lives.” It is also a book a about language and fly-fishing.

A gripping story, beautifully written.

*"An Enquiry Concerning Human Understanding", David Hume, 1748