Everything whose motion is continuous must, on arriving at any point in the course of its locomotion, have been previously also in process of locomotion to that point, if it is not forced out of its path by anything: eg on arriving at a thing must also have been in process of locomotion to, and that not merely when it was near to, but from the moment of its starting on its course, since there can be no reason for its being so at any particular stage rather than at an earlier one.