My research question concerns the relationship between individual interest and common good as this is treated in most of current normative democratic theories. In particular, I want to enquire how political knowledge and motivation to act relate to each other. Consequently, I intend in the first place to tackle the meta-ethical debate about internalism or externalism of reasons for action and to put in question the widespread idea that knowledge is not per se sufficient to motivate action. In the second place, I want to consider the opposition between the general, impartial (neutral) point of view and the personal one, in order to seek whether there is a credible objective notion of one’s individual interest and how this can work, if it works, to constitute a common conception of the interest of all. Finally I focus my research on recent democratic theories, not only because they are the theoretical tools nowadays democratic governments have to use to legitimize themselves, but also because democratic regimes put their citizens in the need and duty to choose between their personal interest and the general one both as subjects and as legislators.