  In one curious respect that Newton mentions only once in passing, the theory does not cover all “conditions that may be supposed.” Newton's theory treats centripetal forces that vary only with the distance from the force center, that is, ones for which the force on two bodies equally distant from that center is always the same. It does not treat centripetal forces that vary with θ and φ, the two angular components of (r, θ, φ) spherical coordinates. This is notable for two reasons. First, the central forces arising in Cartesian vortices would almost certainly have varied with both of these angular components, and hence Newton is tacitly begging a question. Second, as Newton himself realized and noted in Section 13 of Book 1, gravity around a spheroid does not vary simply as 1/r2, but must also vary with  latitude.[33] From Newton's point of view, therefore, gravity around Jupiter and the Earth, and surely the Sun as well, does not vary simply as 1/r2. This is one of many often ignored cues pointing to the extent to which the evidential reasoning in the Principia has to be more intricate and subtle than was appreciated at the time, or for that matter even now.