The nineteenth century saw an increasing separation between the treatment of the surface and the structure of designed objects. Mass production and a mobile market economy encouraged the production of heavily ornamented yet cheaply fabricated products. Affordable manufacture allowed the burgeoning middle class to acquire “luxury” goods fashioned after objects formerly reserved for an elite.
Put together with odd bits of the useless Clarice, a survivors’ Clarice was taking shape, all huts and hovels, festering sewers, rabbit cages. And yet, almost nothing was lost of Clarice’s former splendor; it was all there, merely arranged in a different order, no less appropriate to the inhabitants’ needs than it had been before.
The idea of overlap, ambiguity, multiplicity of aspect, and the semilattice are not less orderly than the right tree, but more so. They represent a thicker, tougher, more subtle and more complex view of structure.
Most objects which we are accustomed to call beautiful, such as a painting or a tree, are single-purpose things, in which, through long development or the impress of one will, there is an intimate, visible linkage from fine detail to total structure.
The resistant virtues of the structure that we make depend on their form; it is through their form that they are stable and not because of an awkward accumulation of materials. There is nothing more noble and elegant from an intellectual viewpoint than this; resistance through form.
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.