to another. Here I only want to point out what has basically already been admitted by

mathematicians, namely: (1) that the Newtonian formulas can be derived from Keplerian laws; (2)

that the Newtonian proof of the proposition that a body governed by the law of gravitation moves

in an ellipse around the central body proceeds in general in a conic section, whereas the main point

that was to be proven consists precisely in this, that the course of such a body is neither a circle

nor any other conic section, but solely the ellipse. The conditions which make the course of the

body into a specific conic section are referred back to an empirical condition, namely, a particular

situation of the body at a specific point in time, and to the contingent strength of an impulse which