



The worst kind of assumptions are the ones that are subtly ingrained in us over a long period of time. It's easy to question a new piece of information that doesn't fit into our existing model of the world, but it's difficult to reflect back to find the incorrect assumptions we're already making. Take for example, the concept of a living thing. We all have a clear understanding as to what is alive and what is not.



The actual The actual definition of a living thing is that the thing must satisfy most of the following constraints:





Homeostasis - Regulation of the internal environment to maintain a constant state

Organization - Being structurally composed of one or more cells.

Metabolism - Ability to transform and consume energy

Growth - Maintenance of a higher rate of anabolism than catabolism.

Adaptation - Ability to change over time in response to the environment.

Response to stimuli

Reproduction - The ability to produce new individual organisms, either asexually or sexually.



Using this definition, a city is a living thing. You can think of utilities as the functions for keeping homeostasis and for metabolism. A city regulates its internal state using utilities like sewage services, law enforcement, and maintenance work. A city consumes electricity, water, food, gasoline, and other natural fuels. It turns the work that its cells (us humans) provide into energy. Cities are built, using work to locally decrease entropy; they grow organically, turning raw materials into meaningful structures. A successful city, like any other organism, will adapt over time in response to its environment, or it will die out. Finally a city can reproduce; the cells from one or more city can leave to form a new city; taking some of the knowledge from the previous cities.



The definition becomes increasingly convoluted as we try to exclude things like cities and software systems from the private club that is our mental model of living things.