This book is the integrated presentation of a large body of work on understanding the operation of biological brains as systems. The work has been carried out by the author over the last 22 years, and leads to a claim that it is relatively straightforward to understand how human cognition results from and is supported by physiological processes in the brain. This claim has roots in the technology for designing and manufacturing electronic systems which manage extremely complex telecommunications networks with high reliability, in real time and with no human intervention. Such systems perform very large numbers of interacting control features. Although there is little direct resemblance between such systems and biological brains, the ways in which these practical considerations force system architectures within some specific bounds leads to an understanding of how different but analogous practical considerations constrain the architectures of brains within different bounds called the Recommendation Architecture. These architectural bounds make it possible to relate cognitive phenomena to physiological processes.