We are thus brought, by a close examination of facts, rather to the idea that the properties of the ether are not wholly reducible to the rules of ordinary mechanics.
The physicist has therefore not yet succeeded in answering the question often put to him by the philosopher: "Has the ether really an objective existence ?" However, it is not necessary to know the answer in order to utilize the ether.

In its ideal properties we find the means of determining the form of equations which are valid, and to the learned detached from all metaphysical prepossession this is the essential point..