In the context of his studies on one of the great productive periods of European thought, Tönnies (1855-1936) edited approximately 60 letters from that time, most of which were previously unpublished. In examining them, he traced the connections between such eminent philosophers as Galileo, Descartes, Mersenne, Gassendi, Hobbes, Spinoza and Leibniz. For Tönnies, the light thrown upon the common intentions of these philosophers is focused on Hobbes.