The objects of our perception invariably include places and times in combination. Nobody has ever noticed a place except at a time, or a time except at a place. But I still respect the dogma that both space and time have independent significance. A point of space at a point of time, that is a system of values x, y, z, t, I will call a world-point.

The Principle of Relativity: A Collection of Original Memoirs on the, Special and General Theory of Relativity, Space and Time (p. 76)