My own book may be crap, but I am certain, when such an imbalance in profitability as the one I have just described emerges, between photojournalism and selfies, that it is all over. This is not a critical judgment. I am not saying that the photos of Pol Pot are good and the selfies are bad. I am saying that the one reveals a subject and the other reveals an algorithm, and that when everything in our society is driven and sustained in existence by the latter, it is all over.
Wang tiles (Hao Wang, 1961) are a class of formal systems. They are modelled visually by square tiles with a color on each side. A set of such tiles is selected, and copies of the tiles are arranged side by side with matching colors, without rotating or reflecting them.
The basic question about a set of Wang tiles is whether it can tile the plane or not, i.e., whether an entire infinite plane can be filled this way. The next question is whether this can be done in a periodic pattern.
In 1966, Wang's student Robert Berger solved the problem in the negative. He proved that no algorithm for the problem can exist, by showing how to translate any Turing machine into a set of Wang tiles that tiles the plane if and only if the Turing machine does not halt. The undecidability of the halting problem then implies the undecidability of Wang's tiling problem.
Picture a blind man probing his way with a cane. While he is alert to the feelings in the hand holding the cane, the crucial distinction may be defined by saying that these feelings are not watched in themselves, but that he watches something else by way of them, that is, by keeping aware of them. He has a subsidiary awareness of the feelings in his hand, feelings which are merged into a focal awareness at the end of the cane, constituting two kinds of awareness that are mutually exclusive — "from awareness" and "focal awareness".
There is here a particularly interesting phenomenal transformation. The sensations of the cane on his hand (the surface of the cane as it touches the palm of his hand, etc.) are lost. Instead, he feels the end of the cane as it touches an object...If our blind man shifts his attention from the tip of his cane to his hand, the meaning on the end of the cane disappears.