You are quoting an extract from a personal letter he wrote to the wife of his recently deceased close friend Michele Besso. My guess is he was saying something totally different to what you think it means and its meaning is a personal one meant as consoling words, not a a scientific one.
That's indeed your personal guess.
I know what Einstein wrote:
<< Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. >> (Albert Einstein, "Relativity", 1952).
<< From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space).
<<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245).
In case you doubt;
Karl Popper about his encounter with Einstein:
<< The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. He agreed that this had been his view, and while discussing it I called him "Parmenides".... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).
And Einstein believed in physics when he said his famous quote:
<<People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion." Einstein died one month and 3 days after his friend, on 18 April 1955.>>
Edited by VandD, 7 January 2017 - 03:29 PM.