"The learned authorities in the world today suppose that there is no harm in mixing extraneous practices with the practice of the Lotus Sutra, and I, Nichiren, was once of that opinion myself. But the passage from the sutra [that I have just quoted] does not permit such a view. Suppose that a woman who had been the consort of a great king and had become pregnant with his seed should then turn round and marry a man of common stature. In such a case, the seed of the king and the seed of the commoner would become mixed together, and as a result, the aid and assistance of heaven and the protection of the patron deities would be withdrawn, and the kingdom would face ruin. The child born from two such fathers would be neither a king nor a commoner, but someone who belongs not to the human realm.
This is one of the most important points in the Lotus Sutra. The doctrine of the sowing of the seed and its maturing and harvesting is the very heart and core of the Lotus Sutra. All the Buddhas of the three existences and the ten directions have invariably attained Buddhahood through the seeds represented by the five characters of Myoho-renge-kyo. The words Namu Amida Butsu are not the seeds of Buddhahood, nor can the mantras or the five precepts act as such seeds. One must be perfectly clear about this point, because this is the fault referred to as being mixed."'