The book emphasizes that intelligence is best understood through behavior. Unlike traditional AI, which focuses on programming computers to perform specific tasks, behavior-based intelligence looks at how intelligent behavior emerges from the interaction between an agent and its environment. This approach is more aligned with how natural intelligence, such as that of humans and animals, operates.

This concept is central to the book and refers to the idea that intelligence cannot be separated from the physical body of the agent. The authors argue that the body plays a crucial role in shaping the mind and that understanding intelligence requires studying the physical interactions between the body and the environment. This perspective challenges the traditional view that intelligence is purely a computational process.

The book advocates for a synthetic approach to understanding intelligence, which involves designing and building artificial systems to test theories about natural intelligence. This hands-on methodology allows researchers to explore how different design principles affect the behavior of intelligent agents. By constructing and experimenting with these systems, researchers can gain deeper insights into the principles that govern both natural and artificial intelligence.