This is water. We are fish in a sea of sense. – David Foster Wallace and William James on the reality of invisibility and the urgency of perception
There are these two young fish swimming along and they happen to meet an older fish swimming the other way, who nods at them and says “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes “What the hell is water?”
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The point of the fish story is merely that the most obvious, important realities are often the ones that are hardest to see and talk about…
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It is about the real value of a real education, which has almost nothing to do with knowledge, and everything to do with simple awareness; awareness of what is so real and essential, so hidden in plain sight all around us, all the time, that we have to keep reminding ourselves over and over:
“This is water.”
“This is water.”
Hold a tumbler of water a little above your eyes and look up through the water at its surface–or better still look similarly through the flat wall of an aquarium. You will then see an extraordinarily brilliant reflected image say of a candle-flame, or any other clear object, situated on the opposite side of the vessel. No candle-ray, under these circumstances gets beyond the water’s surface: every ray is totally reflected back into the depths again. Now let the water represent the world of sensible facts, and let the air above it represent the world of abstract ideas. Both worlds are real, of course, and interact; but they interact only at their boundary, and the locus of everything that lives, and happens to us, so far as full experience goes, is the water. We are like fishes swimming in the sea of sense, bounded above by the superior element, but unable to breathe it pure or penetrate it. We get our oxygen from it, however, we touch it incessantly, now in this part, now in that, and every time we touch it we are reflected back into the water with our course re- determined and re-energized. The abstract ideas of which the air consists, indispensable for life, but irrespirable by themselves, as it were, and only active in their re-directing function.
Lebenskünstler 
Brilliant catch.