"Insofar as man considers himself within the world of natural things and events, he will find it impossible to escape the conclusions of [Einstein's] theory of relativity. But if he does not want to lose himself in mere relativities, in what may be called an impotence of his inner life, if he wants to experience his own entity, he must not seek what is 'substantial in itself' in the realm of Nature, but in [the realm] of transcending Nature, in the realm of the spirit.

       "It will not be possible to evade this theory of relativity for the physical world, but precisely this fact will drive us to a knowledge of the spirit. What is significant about the theory of relativity is the fact that it proves the necessity of a science of the spirit that is to be sought in spiritual ways, independent of observation in nature. That the theory of relativity forces us to think in this way constitutes its value within the development of world conception."

Rudolf Steiner, The Riddles of Philosophy