In this passage, the author argues that a city is a natural system. He believes that human beings are part of nature and there is nothing unnatural about altering environments to build shelter. He cites several examples of this theory. First he points out the flawed argument that cities are unnatural because it disrupts the balance of nature and are inherently evil. He points out that humans are in fact a part of nature and that building shelters is a natural process. The author supports his position by pointing out that even a downtown area has parallels in nature. For example, the buildings in Manhattan are similar to how a forest can be exchanged for a cliff near the ocean. Another example is how both cities and nature have energy sources. Both use sun light and create waste that serves as food sources. The author provides a vivid example how bees use soda as an energy source. Cities also have their own unique collection of flowers and trees and the author supports his claim by noting the new field of urban ecology.

After providing specific examples and clear reasoning, the author provides a broader perspective and argues that cities, like natural ecosystems, grow, evolve and die. Both have life cycles.

Finally the author claims that both cities and natural systems are guided by well defined laws of nature at the atomic level. The central point is that cities can be studied the same way as natural systems.

In the course of framing his argument the author poetically blends clear reasoning and factual descriptions with a sense of optimistic enthusiasm. By putting the word unnatural and nature in quotes he’s pointing out how the terms are often misused. He is respectful of the other sides’ argument but  offers a direct challenge to its position. His tone is resolute but not condescending. Finally his rhetorical style is that of a teacher of who wants to inspire rather than upbraid.

The author successfully conveys his message using the combination of facts, reasoning and emotion. His words and sentence structure are concise, conversational and compelling.