Aśvaghoṣa is 12th in a line of 51 patriarchs linking the Buddha in India and Dogen in Japan, all of whom, according to Zen tradition, preached the primacy of sitting-meditation (ZA-ZEN; sitting-dhyāna).
In the Zen teaching of Dogen, represented by the famous phrase "just sitting," (SHIKAN-TAZA) there is no subject of meditation other than sitting itself: upright sitting is the meditation, and the meditation is to sit upright. Other than sitting itself, there aren't any meditation techniques.
In Canto 16 of the Saundara-nanda of Aśvaghoṣa, however, when the Buddha instructs Nanda how, having found solitude in the forest, to go about working on himself, the Buddha guides Nanda in the appropriate use of a nimitta.
EH Johnston in a footnote to his translation writes, “nimitta, properly the general characteristic of an object, is used of the general characteristic of an object selected to secure any particular type of bhāvanā and so may be translated as [subject of meditation]."
The context of Canto 16 is that the Buddha is instructing Nanda how a sitting practitioner who has already gained possession of the four dhyānas (stages of meditation) and duly acquired the five powers of knowing, then applies his mind to eradicating the āsravas, those influences which pollute the practitioner's mind and prevent him from fully appreciating the four noble truths. The practitioner prevails over these influences, the Buddha tells Nanda, by means of bhāvanā – a term which is generally lumped together with dhyāna and translated as “meditation.”
Thus, by methodically taking possession of the mind,
Getting rid of something and gathering something together,/
The practitioner makes the four dhyānas his own,
And duly acquires the five powers of knowing: //16.1//
The principal transcendent power, taking many forms;
Then being awake to what others are thinking;/
And remembering past lives from long ago;
And divine lucidity of ear; and of eye. //16.2//
From then on, through investigation of what is,
He applies his mind to eradicating the polluting influences,/
For on this basis he fully understands suffering and the rest,
The four true standpoints: //16.3//
This is suffering, which is constant and akin to trouble;
This is the cause of suffering, akin to starting it;/
This is cessation of suffering, akin to walking away.
And this, akin to a refuge, is a peaceable path. //16.4//
Understanding these noble truths, by a process of reasoning
While getting to know the four as one,/
He prevails over all the influences, by means of meditation (bhāvanayā, inst. sg.)
And, on finding peace, is no longer subject to becoming.//16.5//
For by failing to wake up and come round
To this four, whose substance is what is,/
Humankind goes from existence to existence without finding peace,
Hoisted in the swing of saṁsāra.//16.6//
Among multiple definitions of bhāvanā in the Monier Williams Sanskrit-English Dictionary7 are: “1. the act of producing or effecting; 2. forming in the mind, thought, meditation; 3. reflection, contemplation (with Buddhists said to be of five kinds); and 4. water.”
In light of extensive knowledge of ancient Buddhist texts, Ānandajoti Bhikkhu asserts that “the idea of using meditation (bhāvanā) to overcome defilements is very well established in early Buddhism.” This assertion would seem to be supported by Aśvaghoṣa's use of the term bhāvanā in Canto 15, when he quotes the Buddha comparing bhāvanā to water that can put out a smouldering fire:
If some desirous idea, a fever of the mind,
Should venture to offend you,
Entertain no scent of it but shake it off
As if pollen had landed on your robe.//15.3//
Even if, through insight,
You have dropped off desires,
You must, as if lighting up darkness,
Abolish them by means of their opposite.//15.4//
What lies behind them sleeps on,
Like a fire covered with ashes;
You are to extinguish it, my friend, by means of meditation (bhāvanayā),
As if using water to put out a fire.//15.5//
What is problematic for a devotee of “just sitting,” is the principle of sitting cross-legged and using particular types of meditations to overcome specific defilements, as opposed to the indirect principle of just sitting for the sake of sitting, and letting defilements come out, as it were, in the wash.
EH Johnston's translation of nimitta as “subject of meditation,” rests upon his understanding of a direct correspondence between various types of nimitta and particular types of bhāvanā. It is in the process of developing a particular type of bhāvanā, according to Johnston's explanation, that a specific nimitta , or "subject of meditation" is employed.
To glean some understanding of where EH Johnston was coming from, let us consider what the ancient Pali texts have to say about the development of bhāvanā, taking as our starting point the traditional practice of contemplating impermanence, suffering, and non-self.
In Canto 17 of Saundara-nanda, Aśvaghoṣa describes how Nanda, sitting upright with legs crossed, contemplates the elements of earth, water, fire, and so on, as being impermanent, unsatisfactory, and impersonal. By this means, Aśvaghoṣa tells us, Nanda causes the tree of the afflictions to shake (17.17). This is in accordance with what the Buddha tells Rāhula in The Long Discourse Giving Advice to Rāhula. In this ancient Pali text the Buddha instructs Rāhula, in a step preliminary to the development of bhāvanā, to see the elements of earth, water, fire, and so on, as they really are:
Whatever there is, Rāhula, that is inside, in oneself, that is hard or has become solid, and is attached to, like this: head hairs, body hairs, nails, teeth, skin, flesh, sinews, bones, bone-marrow, kidney, heart, liver, pleura, spleen, lungs, intestines, mesentery, undigested food, excrement - or whatever else there is that is inside, in oneself, that is hard, or has become solid, and is attached to, that, Rāhula, is called the internal earth element. Now, that which is the internal earth element, and that which is the external earth element, that is only the earth element. “This is not mine, I am not this, this is not my self,” like this it ought to be seen, as it really is, with right wisdom. Having seen it like this, as it really is, with right wisdom, one loses interest in the earth element, one detaches the mind from the earth element.
The Buddha continues in the same vein, describing as “not my self” the other elements of water, fire, wind, and space. He then exhorts Rāhula to progress further and, with regard to the earth element, to develop bhāvanā, thus:
Develop the meditation (bhāvanaṁ bhāvehi), Rāhula, that is to be even as the earth, for, Rāhula, from developing the meditation that is to be even as the earth, appealing and unappealing contacts that have arisen in the mind will not take a hold there. Just as, Rāhula, they throw what is clean on the earth, and they throw what is unclean, and they throw what has become dung, and they throw what has become urine, and they throw what has become spit, and they throw what has become pus, and they throw what has become blood, but the earth is not distressed, or ashamed, or disgusted by it, just so do you, Rāhula, develop the meditation that is to be even as the earth, for, Rāhula, from developing the meditation that is to be even as the earth, appealing and unappealing contacts that have arisen in the mind will not take a hold there.
Continuing in like fashion for the other elements of water, fire, wind, and space, the Buddha points out that water is not worried about what it washes, fire about what it burns, and wind about what it blows over, while space does not settle anywhere.
Thus, if we follow EH Johnston's line of reasoning, we can understand that the nimitta in question is the general characteristic that all the elements share, which is not to react emotionally, whatever the circumstance. The nimitta is a general characteristic shared by all the elements, and there is one bhāvanā in view, i.e, the meditation that is to be even.
As the Long Discourse continues, however, the Buddha evidently exhorts Rāhula further to develop six bhāvanas:
Develop the meditation, Rāhula, that is friendliness, for, Rāhula, from developing the meditation that is friendliness, whatever ill-will there is will be given up. Develop the meditation, Rāhula, that is kindness, for, Rāhula, from developing the meditation that is kindness, whatever violence there is will be given up. Develop the meditation, Rāhula, that is gladness, for, Rāhula, from developing the meditation that is gladness, whatever discontent there is will be given up. Develop the meditation, Rāhula, that is equanimity, for, Rāhula, from developing the meditation that is equanimity, whatever resentment there is will be given up. Develop the meditation, Rāhula, on the unattractive, for, Rāhula, from developing the meditation on the unattractive (asubhaṁ bhāvanam), whatever passion there is will be given up. Develop the meditation, Rāhula, that is the perception of impermanence, for, Rāhula, from developing the meditation that is the perception of impermanence, whatever (kind of) ‘I am’ conceit there is will be given up.
Still following EH Johnston's argument, we can understand that the Buddha has here enumerated six bhāvanās each with a corresponding nimitta, namely friendliness, kindness, gladness, equanimity, the unattractive, and impermanence.
Subsequently, when we read in Saundara-nanda 16.63 that the Buddha taught Nanda to resort, at a time of heightened passion, to aśubham nimittam (a nimittam which is unattractive, disagreeable or impure), knowledge of the ancient Pali text would naturally tend to lead us to understand that aśubham nimittam belongs to what is described in the The Long Discourse Giving Advice to Rāhula as asubhaṁ bhāvanam (meditation on the unattractive/disagreeable/impure). Hence the following translations of Saundara-nanda 16.63:
But when the mind is excited by passion, the subject of meditation called 'impure' (a-śubham nimittam) should be selected so as to reach steadfastness; for thus the man of passionate nature obtains relief, like the man subject to phlegm who uses astringent remedies.
When the mind is stirred up by passion, one should find stability and practice the impurity meditation (a-śubham nimittam), for that is how a man of passionate nature finds relief, like a patient with a phlegm condition using astringent treatments.
In this understanding, then, a subject of meditation (nimitta) is specifically linked to the development of a particular type of meditation (bhāvanā), with the aim of overcoming a specific defilement.
The essential oneness of sitting-meditation (in Japanese: ZA-ZEN) is Dogen's fundamental teaching, and I would like to think that it is Aśvaghoṣa's fundamental teaching too.
As I said above, the approach to defilements of a devotee of "just sitting," as I understand it, is an indirect one: Just sit, accepting and using the whole self well, and let everything come out in the wash.
But when I re-read Canto 16 and survey the textual evidence impartially, Aśvaghoṣa almost seems to be making a point of falsifying my generalist idea:
Just as a physician, for a disorder of bile, phlegm, or wind,
-- For whatever disorder of the humours has manifested the symptoms of disease --
Prescribes a course of treatment to cure that very disorder,
So did the Buddha prescribe for the faults. //16.69//
So I go into the New Year with a sense that something is not adding up, and a sense that there is work to do -- very probably in the direction of abandoning a cherished idea.