The Cybernetic Brain is a strange, wonderful, and frustrating book. Beautifully written, passionately argued, and based on a decade’s worth of research, the book presents a detailed, wide-ranging history of British cybernetics as a usable past to challenge how we think about science and modernity. A sociologist of science who has written landmark books on quarks and ‘‘posthumanist’’ science studies, Pickering explains that Cybernetic Brain ‘‘is very much my own history of cybernetics in Britain—not a comprehensive survey, but the story of a set of scientific, technological, and social developments that speak to me for reasons I will explain and that I hope will interest others’’ (4). To create his own history of cybernetics, Pickering follows a strand of research extending from the work of two first-generation British cyberneticists—brain scientists W. Grey Walter and W. Ross Ashby—to that of second-generation researchers Stafford Beer and Gordon Pask, a strand that extends from the late 1940s to the 1970s. The psychiatric research of Gregory Bateson and R. D. Laing is considered with the first group. Along this strand, Pickering studies cybernetics in practice rather than the history of ideas, the performative rather than the representational aspect of British cybernetics. He emphasizes, for example, the unpredictable exploratory movements of Walter’s ‘‘tortoises’’ (small-scale electronic robots), rather than Walter’s attempts to use those movements to understand and represent the functioning of the human brain. In this trajectory of research, British cybernetics was transformed from the ‘‘science of the adaptive brain’’ (8) in the early 1950s, as instantiated in Walter’s tortoises and Ashby’s electromechanical ‘‘homeostat’’ model of the brain, into a ‘‘protean science’’ of the 1960s and 1970s, symbolized by Pask’s design of the Fun Palace, an interactive and adaptive architectural project, and Beer’s Project CyberSyn, an interactive computer system built to run the Chilean economy.