We are at one of those turning points that divide history into a ‘before’ and an ‘after.’ The ongoing transition from an information economy to an economy based in the workings of the brain and the mind has radical implications for human freedom and creativity, both of which are under threat from a rapacious form of technological capitalism. Such moments require new languages in order for the unnamed, the unsayable, and the misunderstood to become known. This is the task taken on by Warren Neidich’s Glossary of Cognitive Activism, now appearing in an expanded and fully revised fourth edition. Each of its entries—which range in topic from the central nervous system and brain-computer interfaces to ChatGPT and conceptual art—explicates a key term in contemporary culture. The cumulative effect is astonishing: while every entry can profitably be read in isolation, the Glossary as a whole amounts to a brilliant account of the material brain’s entanglement with its surrounding environment. For Neidich the human brain is far more than grey matter encased in a skull: it is profoundly integrated with the social, political, and cultural phenomena that constitute the world in which we live. For this reason, human cognition is profoundly vulnerable to the new despotism that is seeking in various ways to reshape it, but it also has the capacity to serve as the site of potent acts of resistance. Forging connections between such apparently disparate domains as neuroscience, ecology, political economy, and aesthetics, Neidich’s Glossary restores human cognition to its rightful status: not as the passive object of technological interventions or reductive theorizing, but as the starting point for any viable form of egalitarian and liberatory politics.