How can we understand a system as complex as the brain? Does the brain use the same operational principles to control physical and mental activities? How can we incorporate in a model what we know and what we do not know about the brain?The connectionist model presented in this book provides tools for addressing such questions. Its nodes represent well-established biological facts combined with observations of the overall behaviors of the system. The model is based on comparing and contrasting brains, computers, and neural networks. It defines a framework for understanding the relationships between the brain and the mind. It can serve both as a starting point for developing Artificial Intelligence applications for all levels of mental activities and as a guide in the search for biological correlates of observed behaviors.