The permanence is itself meaningless apart from some immediate judgment of self-congruence.

Otherwise how is an elastic string differentiated from a rigid measuring rod?
Each remains the same self-identical object.

Why is one a possible measuring rod and the other not so?
The meaning of congruence lies beyond the self-identity of the object.

In other words measurement presupposes the measurable, and the theory of the measurable is the theory of congruence.
Furthermore the admission of stratifications of nature bears on the formulation of the laws of nature.

It has been laid down that these laws are to be expressed in differential equations which, as expressed in any general system of measurement, should bear no reference to any other particular measure-system.