[p. 230]: the chief difference [is] that Einstein simply postulates what we have deduced, with some difficulty and not altogether satisfactorily, from the fundamental equations of the electromagnetic field. [p. 321]: The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t′ must be regarded as no more than an auxiliary mathematical quantity. In Einstein's theory, on the contrary, t′ plays the same part as t; if we want to describe phenomena in terms of x′, y′, z′, t′ we must work with these variables exactly as we could do with x, y, z, t.