Indra, the King of the Gods in Hindu Mythology, possesses a number of treasures, one of which is a net made entirely of jewels. According to the Buddha in the Gandavyuha Sutra, “All the Jewels shine in each, and each of them shine in all.”
The universe is just like this. As such, one cannot fully understand any one part of the Dharma unless one understands the whole.
Excerpted from the talk "The Universal Perspective of Mahayana Buddhism" by Sangharakshita, 1971, as part of the series Parables, Myths and Symbols of Mahayana Buddhism in the White Lotus Sutra.