This letter opens up with the original letter from a follower who thinks he's got the Pure Land method figured out after 10 years. He talks of Chan methods like recitation with a dead mind and the koan of "who is it that recites the Buddha's Name?"
The Meditation Sutra teaches: Recite the Mahayana sutras, understand the Supreme Meaning, develop the Bodhi Mind, counsel and exhort others to cultivate. This must certainly be your intention. Nevertheless, the Dharma should be adapted to the level of the listener. If through failure to examine his level, you administer the wrong remedy, you will be no different from an incompetent physician who kills his patients with the wrong medicine. You should know that although the two Dharma methods, Pure Land and Zen, have the same root and the same source, their methods of cultivation are different. The main tenet of Zen is to see one’s Original Nature, while the teachings of Pure Land are Faith, Vows and Reciting the Buddha’s name to achieve rebirth in the Pure Land.
I think the distinction between Zen and Pure Land methods is significant. When the methods get confused, it can cause confusion in practitioner.
those of high capacities are few and far between, while those of moderate and low capacities form the vast majority. This being the case, failing to teach people to develop Faith and Vows seeking rebirth in the Pure Land, while advising them to meditate on the Buddha’s name [as a koan] is utterly detrimental. This is because, while awakening to the Way through meditation on the Buddha’s name would be a fortunate development, an utterly sincere Vow for rebirth in the Pure Land would still be necessary. Meanwhile, if meditation is unsuccessful and the mind constantly grasps at the koan “who is reciting the Buddha’s name,” correspondence between the practitioner and the Buddha will be extremely difficult to realize and the benefit of the “welcoming and escorting” Vow will be lost. Those who really know “who is reciting the Buddha’s name” are precisely those who have already awakened and clearly seen their True Nature. Nowadays, how many practitioners can meditate to the point of awakening to the Way (Great Awakening)?
Faith is fundamental to Pure Land practice. Teachings that bolster faith should be prioritized over teachings that interfere with it or (worse yet) deny its validity & importance. I think this is ultimately the reason why the Pratyutpanna Sutra isn't/wasn't stressed by Pure Land schools - it doesn't stress faith and has some passages that could confuse those who aren't established in their faith. While one who is able to complete the rigorous practices detailed in the Pratyutpanna Sutra might be able to become Awakened to the true nature of mind, those who aren't able to complete the practices will be that much further from establishing the requisite faith.
Since your understanding of the Dharma is not skillfully adapted to people’s capacities, in that you attempt to bring a high-level Dharma to everyone, it is, in the end, a one-sided (biased) attachment – and a great mistake! Not realizing this, you think that you have correctly understood the subtle meaning of the Dharma and therefore seek my certification. This monk, although lowly and not erudite, would not dare to commend, acquiesce in and support such a request, which would cause all of us to fall into the error of vilifying the Three Treasures!
I think this points out another point of Pure Land teachings, as well as their major strength. The strength of these teachings is that they're for simple folk, not only for super meditators or people of super high capacities - everyone can benefit. These teachings are also not about book knowledge. Conceptual knowledge of the sutras & the teachings of the masters does not replace faith, vows, and practice.