My approach to what I do in my job — and it might even be the approach to my life — is that everything I do is the most important thing I do. Whether it’s a play or the next film. It is the most important thing. I know it’s not going to be the most important thing, and it might not be close to being the best, but I have to make it the most important thing. That means I will be ambitious with my job and not with my career. That’s a very big difference, because if I’m ambitious with my career, everything I do now is just stepping-stones leading to something — a goal I might never reach, and so everything will be disappointing. But if I make everything important, then eventually it will become a career. Big or small, we don’t know. But at least everything was important.
A theory of change is the opposite of a theory of action — it works backwards from the goal, in concrete steps, to figure out what you can do to achieve it. To develop a theory of change, you need to start at the end and repeatedly ask yourself, “Concretely, how does one achieve that?”
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.