Theo Verbeek works mainly on early modern philosophy. Within that field he specifically concentrates on Descartes and Cartesianism (especially Dutch Cartesianism), Spinoza and the early Enlightenment.
- Current projects on Descartes focus on editorial problems (together with Dr Erik-Jan Bos he prepares contributions to a new edition of Descartes for the 'Bibliothèque de La Pléiade' and works on a new critical edition of Descartes' Correspondence), translations (Dutch translations of Descartes' passions de l'âme and of a selection of the correspondence), biography (he received an NWO grant for a study of Descartes' scientific network) and methodological and epistemological problems in Descartes' 'scientific' work;
- Since his book on Spinoza's Theologico-political Treatise (Aldershot 2003) there has been a shift of emphasis in the direction of Spinoza's theory of mind and action (relation of imagination, reason and intellect; theory of the imagination; theory of the passions, etc);
- In recent years some of the themes discussed in the PhD dissertation on La Mettrie are being revived, also against the background of a critique of Jonathan Israel's work on the Enlightenment;
- In the planning stage is a work on (mainly Dutch) Cartesianism, which will concentrate on problems of language and communication.