Note Note 7 — III EINSTEIN

Einstein had become tired of assumptions. He had no particular objection to the “ether” theory beyond the fact that this “ether” did not come within the range of our senses; it could not be “observed.” “The consistent fulfilment of the two postulates—‘action by contact’ and causal relationship between only such things as lie within the realm of observation [see Note 2] combined together is, I believe, the mainspring of Einstein’s method of investigation.…” (Prof. Freundlich).