British philosophy is sometimes celebrated and sometimes satirized as sturdy common sense. It tends to be grounded in facts and logic, and prefers science to mysticism. But for a generation or two during the late 1800s and early 1900s, a loose movement called British Idealism came to dominate philosophy in the universities. The major figures – Bradley, McTaggart, Green and Alexander – often disagreed among themselves, but they typically denied the reality of space and time, claiming that the world of science and appearance was contradictory. They believed instead in some sort of higher, spiritual reality. They were rational mystics.

James McTaggart supported his metaphysical idealism by advancing a famous argument against the existence of time. His attack has survived the rest of his philosophy, and continues to be widely discussed. When the argument was first published in 1908, three years after Einstein's papers on special relativity, debates over the nature of time were quite fashionable. Questions about whether time was another “dimension” and whether the world was really a four-dimensional block universe began to emerge. Independently of Einstein's theories, McTaggart saw clearly that such views might be incompatible with real change. If time is like a spatial dimension, he argued, then there is no such process, no “change”, whereby one thing becomes another.

The A-series and the B-series

The truth-maker principle insists that if a sentence is true of the world, then something in the world makes it true.