Reflections on the Missing Shade of Blue

What do we know, and how do we really know what we know? David Hume, the 18th-century Scottish philosopher, ventured that everything we perceive comes from what we’ve directly experienced. If we happen upon a thought, an idea, that we can’t trace back to a sense experience, then that idea cannot really be meaningful. This thinking flies in the face of all rationalist discourse, but Hume was an empiricist, so let’s leave it at that for now.

In what may be the mother of all epistemological WTHs, Hume willingly served up a counterexample, an exception, if you will, to his own ironclad argument that all ideas come from experience. If a man, he hypothesized, has seen all the colors of the world except for one particular shade of blue, and if all the shades of blue were laid out before him—from the darkest to the lightest—except the single shade he’s never before seen, might it be possible for him to conceive of it without having experienced it? (Strangely, Hume said yes, but added that the occasion would be so rare that it didn’t disprove his original rule.)

My first impulse was to say yes as well. Of course the man can imagine the missing blue shade because the mind naturally makes inferences and fills in the blank. But when I put on my empiricist hat, I started to wonder: can I truly, meaningfully know anything if I’ve never seen, heard, touched, tasted, or otherwise experienced it?

I sat with this for a while and ended up going a bit off tangent. For me, the more interesting question lies elsewhere.

How does one know that there was a missing shade of blue to begin with?

Embedded in the question of whether or not one can fill in the blank is an assumption that there exists a shade of blue for which a blank space has been made. And is there not always a gap at the heart of everything we know and can know? We may not know with what we would fill it, or even how we might choose to fill it. But two things I do know with some measure of certainty: that it is there, and that it is in the continuous attempts at filling (what in all likelihood is unfillable) that we constitute all things meaningful.

Philosophers have debated about what possessed Hume to practically invalidate his entire theory of knowledge with this beautifully poetic counterexample. I’m not as baffled. I would hazard a guess that even the strictest and most pragmatic empiricist is wise enough to acknowledge that at the core of human experience is the existence of a hole, the provenance of which we might never know, but with which we have to make a certain kind of peace.