By focusing upon three figures: a trade unionist, who can no longer understand or reconcile himself with his past misogynist behaviour; Spinoza’s Spanish poet, who loses his memory and can no longer write poetry or even recognise his earlier work; and Spinoza’s lost friend, Burgh, who became a devout Catholic, I draw out Spinoza’s description of radical change in beliefs. I explore how, for Spinoza, radical changes that involve an increase in our powers of acting are conceived differently from those changes that reduce our power. These transitions—which can be viewed as both personal and political—are not symmetrical because of the way in which they can be understood in relation to selfhood. To highlight the originality of Spinoza’s argument on personal change, I then compare it with that of his contemporary John Locke, who in Chapter 27 of the Essay Concerning Human Understanding famously theorises the maintenance of personal identity. I draw out one common aspect of the work of Étienne Balibar and of Janet Coleman to compare the ways in which Spinoza and Locke produce different answers to the same questions: how do we conceptualise our encounters with bodies and with ideas? How do these encounters affect our identity over time? In the final section, I switch from analysing personal (but also political) change to consider political change itself, by juxtaposing Warren Montag’s Spinozist analysis of the will, with Carole Pateman’s feminist critique of contract and consent.