) and interprets (
) as space coordinates and
as a measure of time, merely on the ground that some physical law is thereby expressed. This is not an interpretation of what we mean by space and time. What we mean are physical facts expressible in terms of immediate perceptions; and it is incumbent on us to produce the perceptions of those facts as the meanings of our terms.
Einstein has interpreted the Lorentzian formulae in terms of what we will term the 'message' theory, discussed in the next chapter.
[APPENDIX TO CHAPTER III]
Let
and