 Shortly after, Whitehead must have learned about Einstein’s Special Theory of Relativity (STR) because in a letter to Wildon Carr on 10 July 1912, Russell suggested to the Honorary Secretary of the Aristotelian Society that Whitehead possibly might deliver a paper on the principle of relativity, and added: “I know he has been going into the subject”. Anyhow, in the early years of the second decade of the twentieth century, Whitehead’s interest shifted from the logical reconstruction of the Euclidean space of classical physics to the logical reconstruction of the Minkowskian space-time of the STR.