In April 2012 Synthese published a ‘Thematic Section’ of three papers dealing with ‘seeing the causes in Baroque Optics’ a part of the Baroque Science Project conducted between 2006 and 2009 by Ofer Gal, Raz Chen-Morris and colleagues in the School of History and Philosophy of Science, University of Sydney These papers are: •Ofer Gal and Raz Chen-Morris, ‘Nature’s drawing: problems and resolutions in the mathematization of motion’, Synthese, 185 no.3 (2012): 429-466. •John A. Schuster, ‘Physico-mathematics and the search for causes in Descartes’ optics—1619–1637’ Synthese, 185 no. 3 (2012): 467-499. •Sven Dupré, ‘Kepler’s Optics without Hypotheses’, Synthese, 185 no.3 (2012): 501-525. The Thematic Section was supposed to be prefaced by an Introduction, linking the papers to each other and to the Baroque Optics research program. In the event it was not possible to provide the Introduction in the published volume of Synthese. However, John Schuster, elaborating an earlier draft by Ofer Gal, here introduces the papers in the Thematic Section. See also the relevant Schuster paper in this research section.