The similarity of Shingon (Son of Heaven) and Christianity (God)

"Later, in the reign of Emperor Hsüan-tsung, the Tripitaka Master Shan-wu-wei journeyed to China from India, bringing with him the Mahāvairochana and Susiddhikara sutras. In addition, the Tripitaka Master Chin-kang-chih appeared with the Diamond Crown Sutra. Moreover, Chin-kang-chih had a disciple named the Tripitaka Master Pu-k’ung.

These three men were all Indians who not only came from very distinguished families but were in character quite different from the priests of China. The doctrines that they taught appeared highly impressive in that they included mudras and mantras, something that had never been known in China since the introduction of Buddhism in the Later Han. In the presence of this new Buddhism, the emperor bowed his head and the common people pressed their palms together in reverence.

These men taught that, whatever the relative merits of the Flower Garland, Profound Secrets, Wisdom, Nirvana, and Lotus sutras might be, they were all exoteric teachings, the various preachings of the Thus Come One Shakyamuni. The Mahāvairochana Sutra that they had newly introduced, on the other hand, represented the royal pronouncements of the Dharma King Mahāvairochana. The other sutras were the multiple sayings of the common people; this sutra was the unique pronouncement of the Son of Heaven. Works such as the Flower Garland and Nirvana sutras could never hope to reach as high as the Mahāvairochana Sutra even with the help of a ladder. Only the Lotus Sutra bears some resemblance to the Mahāvairochana Sutra.

Nevertheless, the Lotus Sutra was preached by the Thus Come One Shakyamuni and thus represents merely the truth as spoken by a commoner, while the Mahāvairochana Sutra represents the truth as spoken by the Son of Heaven. Hence, although the words resemble each other, the persons who spoke them are as far apart as the clouds in the sky and the mud on earth. The difference between them is like the moon that is reflected in muddy water on the one hand and in clear water on the other. Both alike are reflections of the moon, yet the nature of the water that catches the reflection is vastly different." - On Repaying Debts of Gratitude