"If the astronomical
observations and other quantities on which the computation of orbits were absolutely correct, the elements also, whether deduced from three or four observations, would be strictly accurate (so far indeed as the motion is supposed
to take place exactly according to the laws of Kepler
), and, therefore, if other observations were used, they might be confirmed but not corrected.
But since all our measurements and observations are nothing more than approximations to the truth
, the same must be true of all calculations resting upon them, and the highest aim of all computations made concerning concrete phenomena must be to approximate, as nearly as practicable, to the truth
. But this can be accomplished in no other way than by a suitable combination of more observations
than the number absolutely requisite for the determination of the unknown quantities. This problem can only be properly understood when an approximate knowledge of the orbit has been already attained, which is afterwards to be corrected so as to satisfy all the observations in the most accurate