These days the practice of the nembutsu is being entangled in vigorous debate over the doctrines of once-calling and many-calling. This debate touches on matters of crucial importance and demands that we exercise great care. Both the advocacy of a position of once-calling that rejects many-calling and the advocacy of many-calling in denunciation of once-calling run counter to the essential meaning of the Primal Vow and fail to take into account the teaching of Shan-tao.
Many-calling is nothing but the accumulation of single callings, for human life is such that a person should consider each day that this may be his last, each minute that this may be the end. From the very moment of our birth, this realm of impermanence is merely a fleeting and temporary dwelling; our lives may be compared to a lantern flame before the wind, or likened to dew upon a blade of grass, and there is no escape anywhere for even a single person, whether wise or foolish, from the extinction of breath and the draining away of life. If our eyes may close forever even in this present instant, then we say Namu-amida-butsu, aspiring to be saved by Amida’s Primal Vow and welcomed into the Pure Land of perfect bliss, based on our trust in the supreme virtues embodied in a single calling and our reliance on the great and vast benefit of that one calling.
As life continues, this single calling becomes two or three callings; they accumulate, so that one moment becomes an hour, then two hours; a day or two; a month, a year, two years, ten or twenty years, eighty years. The immutable nature of our existence is expressed truly in the statement that we should wonder how it is that we are still alive today, and whether this very instant will be our last in this world. Therefore, Shan-tao prays, “May all people constantly desire that the excellent conditions and surroundings appear before them at the time of death,” earnestly encouraging us to say the nembutsu from moment to moment, neither forgetting nor neglecting it for even a single instant, until the time we are actually born in the Pure Land. If a person maintains that many-calling is necessary, even though there is no many-calling separate from once-calling, nor any once-calling apart from many-calling, then surely he is a greater enemy of the Pure Land teaching than those who simply ignore such passages of the Larger Sutra of Immeasurable Life as the one that teaches:
When sentient beings hear the Name, say it even once in trust and joy, sincerely turn over their merits [toward attainment of birth], and aspire to be born in that land, then they shall attain birth and shall dwell in the stage of nonretrogression.
Or the one that reveals that
If a person thinks on that Buddha even once, he will attain birth.
Or the one that declares beyond doubt:
If there are persons who, having heard the Name of that Buddha, leap and dance with joy and say it even once, know that they receive the great benefit; that is, they acquire the unexcelled virtues.
Or also those of Master Shan-tao, who, in accord with the intentions of the sutra, determined:
Saying the Name even once in joy, all attain birth.
With ten voicings or one voicing – a single utterance – all decisively attain birth.
If, however, because of belief in this, you adhere single-mindedly to the position of birth through once-calling and declare that many-calling is erroneous, then do you intend to overlook the words of the Primal Vow, “Saying the Name perhaps even ten times,” and ultimately take the teaching of saying the Name for one to seven days in the Smaller Sutra to be pointless? Do you also regard as erroneous the teaching of Master Shan-tao? Based on these sutra passages, he instructs us to practice without interruption for a long period of time:
Single-heartedly practicing the saying of the Name of Amida alone – whether walking, standing, sitting, or reclining – without regard to the length of time, and without abandoning it from moment to moment: this is called “the act of true settlement,” for it is in accord with the Buddha’s Vow.
Vow that to the end of this life there will be no retrogressing, and that you will make the Pure Land your single goal.
To break with Shan-tao’s teaching and slander it after having once entered the Pure Land gate is to be an even greater enemy than people of other teachings and different understandings. Such people, forever remaining as stragglers in the three courses, have no chance of emerging; it is wretched. Hence it is taught:
The Buddha comes to welcome those who, at the upper limit, spend their entire lives in the nembutsu,
Down to those who say it only ten or three or five times.
Solely through the greatness of the universal Vow,
Foolish beings, when they become mindful of it, are brought to attain birth.
And further, one truly knows now, without so much as a single thought of doubt, that Amida’s universal Primal Vow decisively enables all to attain birth, including those who say the Name even ten times, or even but hear it.
Those who say the Name for seven days or one day, down to ten voicings or one voicing – a single utterance – will unfailingly attain birth.
These passages teach beyond all doubt that there should be no controversy over the positions of once-calling and many-calling; the person who has simply entrusted himself to Amida’s Vow should continue to say the nembutsu until the end of his life, with birth in the Pure Land as his goal. You must not cling to one or the other extreme. I have been unable to express my innermost thoughts as I would like; still, I hope the reader will be able to grasp my meaning through these notes.
Those who adhere to once-calling as well as those who cling tenaciously to many-calling invariably meet with inauspicious deaths, for both deviate from the meaning of the Primal Vow. Consider this carefully. It cannot be said too often that you must avoid confusing the truth that many-calling is itself once-calling and that once-calling is many-calling.
Kencho 7 
Fourth month, 23rd day
Gutoku Shaku Zenshin