Even here on earth, with our senses seemingly full to the brim, we see almost nothing of what matters. Molecules, microbes, cells, germs, genes, viruses, the interior of the planet, the depths of the ocean: none of that is visible to the naked eye. And, as David Hume noted, none of the causes controlling our world are visible under any conditions; we can see a fragment of the what of things, but nothing at all of the why. Gravity, electricity, magnetism, economic forces, the processes that sustain life as well as those that eventually end it—all this is invisible. We cannot even see the most important parts of our own selves: our thoughts, feelings, personalities, psyches, morals, minds, souls.from a review by Kathryn Schulz of Invisible: The Dangerous Allure of the Unseen by Philip Ball.
At the beginning of the book Ball quotes from Heart of Darkness by Joseph Conrad:
And perhaps in this is the whole difference; perhaps all the wisdom, and all the truth, and all sincerity are compressed into the inappreciable moment in time in which we step over the threshold of the invisible.
Image: Georges Seurat