The project aims to trace the development of Wittgenstein’s second book project laying the foundations for a principled view of the origin of the Philosophical Investigations. The idea is to yield an adequate view of what belongs in the Philosophical Investigations corpus, while at the same time showing what its status is. In this way, the connections between the philosophy of culture and mind and the philosophy of psychology, on one hand, and between these and the philosophy of mathematics, on the other, as spread among Wittgenstein’s various projects for the Philosophical Investigations, will be re-evaluated. The majority of these sources have been available since 2000 in the Bergen Electronic Edition of Wittgenstein’s Nachlass, but we are still in need of a thorough examination of them. In addition, new items have come to light in the meantime which justify a close study. It is such a philological-philosophical study that the project aims to carry out, analysing the genesis of Wittgenstein’s Philosophical Investigations and also editing hitherto unpublished texts. Our understanding of the Philosophical Investigations project and its relation to other Nachlass parts and periods will be significantly improved, and this will make it possible to establish its potential for continued influence on 21st century thought in ways that are anchored to a secure text basis. This objective will be achieved in close cooperation with the Wittgenstein Archives at the University of Bergen (WAB).