Descartes's La Géométrie transformed the relationship between figures and equations by showing that any geometric curve could be expressed as an algebraic equation and vice versa. That union created the conceptual space of calculus: variation, slope, and area could now be thought of over algebraized objects. Published as an appendix to the Discours de la Méthode, it is probably the most decisive conceptual link between Viète's symbolic algebra and the calculus of Leibniz and Newton.