The role of cortex in the execution and learning of behaviour remains unclear, particularly in lower mammals (e.g. rodents). My lab studies the cortex of rodents; we design new behavioural assays and new electrode technologies for recording from distributed populations of neurons. In a typical seminar talk, I would present an overview of my lab’s work and highlight our exciting progress in clarifying the function of cortex. This usually takes about an hour, but if there is time remaining, then I also like to introduce (and briefly speculate answers to) some of the outstanding questions: what behaviours require cortex? why are these different between primates and other mammals? what does this tell us about the role (and origin) of cortex? Cortex Club is not a typical seminar series. Therefore, I have decided to expand these “final 5 minutes of speculative brainstorming” into the majority of my presentation. I will present work from my lab, but also that of many others over the past 150 years, to motivate explicit proposals for the teleology of mammalian cortex.