   A third aspect of the new method, which proved most controversial at the time, was the willingness to hold questions about the mechanism through which forces effect their changes in motion in abeyance, even when the mathematical theory of the species and proportions of the forces seemed to leave no alternative but action at a distance. This aspect remained somewhat tacit in the first edition, but then, in response to criticisms it received, was made polemically explicit in the General Scholium added at the end of the second edition: