Kant's radical criticism of the passions has a central but largely overlooked moral-psychological component: for Kant, the passions promote a kind of self-deception he calls ‘rationalizing’. In analysing the connection between passion and rationalizing self-deception, I identify and reconstruct two essential traits of Kant's conception of the passions. I argue (1) that rationalizing self-deception, according to Kant, contributes massively to the emergence and consolidation of passions. It aims to resolve a psychological conflict between passion and moral duty when in fact, it does not resolve but perpetuates this conflict. I then argue (2) that rationalizing does not necessarily aim to devalue moral duty, as Kant seems to suggest in the Groundwork. It can also aim to revalue the ‘counterweight’. By analysing Kant's presentation of several individual passions in the Anthropology, I demonstrate that rationalizing here is concerned with elevating these passions and making them pass as morally (or at least prudentially) justified.