"But the cause that impels them to leave life as a human being and to sink down into the evil realms is not always the same in all cases. Some do so because of their pity and fondness for their wives and children or their other household members; some because of the grave karma they have created by killing living beings or committing other evil deeds; some because, having become rulers of a nation, they fail to heed or understand the afflictions of the populace; some because they do not distinguish between the correct doctrine and one that is erroneous; and some because they put their trust in evil teachers.
Among these various causes, those that pertain to the rights and wrongs of everyday behavior are readily apparent, and even a foolish person can judge what is proper conduct. But when it comes to determining what is correct or incorrect in matters of Buddhist doctrine or distinguishing between good teachers and evil ones, even a sage who has gained enlightenment as a result of extended religious practice will be at a loss, and how much more so an ordinary person in this latter age!
Moreover, since the Buddha, like the sun, has sunk from sight beyond the western hills, leaving his last rays to shine upon those of us in the eastern regions, the torch of wisdom held up for us by the four ranks of sages has grown daily dimmer, and the doctrinal teachings of the Tripitaka masters have become more corrupt with each passing month. Scholars, confused in their understanding of the true teaching, interpose themselves like clouds before the moon of Truth, and translators of sacred scriptures who are dedicated to the provisional sutras smash to pieces the jewels of the true sutras and reduce them to the rubble of provisional sutras.
Furthermore, there can hardly fail to be errors in the doctrinal principles expounded by the Buddhist teachers of the various schools of China, and it is even more likely that, among the latter-day scholars in this far-off land of Japan, mistakes are manifold and the truth seldom to be found. As a result of all this, though the persons who devote themselves to the study of the teachings are more numerous than the scales of a dragon, those who truly attain the way are rarer than the horn of a ch’i-lin.
Some persons err because they rely upon the provisional teachings, some because they rely on teachings that do not accord with the time or the capacities of the persons addressed. Some go astray because they fail to distinguish between the teachings of sages and those of mere ordinary mortals, some because they fail to distinguish between the provisional teachings and the true teaching, some because they mistake provisional teachings for the true teaching, and some because they do not understand the level of the persons to whom the teachings are directed. Thus these various types of persons in their capacity as ordinary mortals seek the Buddhist teachings but instead only increase the karma that will keep them bound to the sufferings of birth and death, but the exact cause in each case is not necessarily the same." -- Nichiren