The prevalent view provides no such definition.

Its position is that if we take such time-measurements so that certain familiar velocities which seem to us to be uniform are uniform, then the laws of motion are true.

Now in the first place no change could appear either as uniform or non-uniform without involving a definite determination of the congruence for time-periods.

So in appealing to familiar phenomena it allows that there is some factor in nature which we can intellectually construct as a congruence theory.

It does not however say anything about it except that the laws of motion are then true.