Kepler’s half-insight, half-inferential-leap that the orbits were ellipses and not just off-center circles (made possible by the fantastic quality of the data B

Kepler’s half-insight, half-inferential-leap that the orbits were ellipses and not just off-center circles (made possible by the fantastic quality of the data Brahe gathered—he didn’t even have a telescope, remember) was very important to Newton’s positing the law of universal gravitation. (The universal part is much more important here, as far as a naturalist’s worldview is concerned, than the gravitation one.) See Arnold’s writings regarding just how tiny the difference is between the two possibilities. Would Kepler’s absence have stopped scientific progress? Probably not. But some very, very important parts of it would not have proceeded as they did.