Alexander has studied extensively what properties were exhibited by living structures. He compared hundreds, maybe thousands of structures, trying to understand each time what living structures had that lifeless ones had not.
Over time, he came up with a list of 15 properties. These properties are different kind of relationships between centers that help create a living structure. The more the centers of a given design reinforce themselves through these 15 properties, the more life the structure will have.
These properties are the following:
- Levels of scale
- Strong centers
- Alternating repetition
- Positive space
- Good shape
- Local Symmetries
- Deep interlock & ambiguity
- The Void
- Simplicity and Inner Calm
In the meantime, here is a quick overview of some of them:
This tiger face is filled with centers. The eyes and the nose are the Strong Centers of this face. There are many Local Symmetries, starting with that of the whole face. There are Boundaries around the eyes or the nose. There is Contrast in the black and white colors of the fur around the eyes or the nose. There is Alternating Repetition of the stripes. There is Roughness in the fact that the stripes are not perfectly regular or symmetrical.