Even before the problem of Mercury's orbit cropped-up, there was a problem with the apsides of the Moon's orbit which seemed to falsify Newton's theories. Wiki: " Another issue still remained with the three body problem; how the Moon rotates on its apsides. Even Newton could account for only half of the motion of the apsides." While such luminaries as Euler were inclined to deem Newton's Laws as falsified (although the word had not been invented at that stage), Clairaut kept faith with the paradigm, and with a bit of clever mathematics was able to uphold Newtons Laws - and in so doing, provide greatly improved solutions to the 3-body problem.