We extend to general Cartesian categories the idea of Coherent\nDifferentiation recently introduced by Ehrhard in the setting of categorical\nmodels of Linear Logic. The first ingredient is a summability structure which\ninduces a partial left-additive structure on the category. Additional\nfunctoriality and naturality assumptions on this summability structure\nimplement a differential calculus which can also be presented in a formalism\nclose to Blute, Cockett and Seely's Cartesian differential categories. We show\nthat a simple term language equipped with a natural notion of differentiation\ncan easily be interpreted in such a category.\n