Classical Physics had relied for centuries on mechanical models as a supposedly all- sufficient basis for understanding the physical world. (A mechanical model is an image or replica corresponding in some objective way- not merely a metaphorical way- to the thing that it represents.) 'Abdul- Baha stated forcefully that 'nature... in its essence' is utterly incompatible with mechanical models. Its deepest building blocks can no more be expressed by objective description than can such abstractions as 'love' or 'truth'. Such assertions were, at that time, even more daring and radical than 'Abdul- Baha's rejection of material ether. Yet His insights were fully validated, more than fifty years later, by the development of quantum mechanics- the mathematical description of subatomic particles and their behaviour. The resulting collapse of mechanical models lies at the very heart of the revolution in physics which, in this century, has shaken the world, transformed every aspect of modern life, and (in the words of Sir James Jeans) made the universe appear 'more like a great thought than like a great machine'.