the universe can be best pictured, ... as consisting of pure thought, the thought of what, for want of a wider word, we must describe as a mathematic… - James Hopwood Jeans

With the coming of the twentieth century, there came into being a new physics which was especially concerned with phenomenon on the atomic and sub-atomic scale. ...A preliminary glance over the vast territory of this new physics reveals three outstanding landmarks.

The concepts which now prove to be fundamental to our understanding of nature—a space which is finite; a space which is empty, so that one point [of our 'material' world] differs from another solely in the properties of space itself; four-dimensional, seven- and more dimensional spaces; a space which for ever expands; a sequence of events which follows the laws of probability instead of the law of causation—or alternatively, a sequence of events which can only be fully and consistently described by going outside of space and time—all these concepts seem to my mind to be structures of pure thought, incapable of realisation in any sense which would properly be described as material.

An extension of Planck's ideas, due to Prof. Niels Bohr of Copenhagen, went on to suggest that... the ultimate particles of matter would be seen to move not like railway trains running smoothly on tracks, but like kangaroos hopping about in a field.