The fullest Sutta description of the kāyasakkhi, ditthipatto, and saddhāvimutto (referred to hereafter as k, d and s) is given in the Kītāgiri Sutta, M. 70: i,477-78. The k is described as an individual who has reached the arūpa attainments and dwells therein, and, having seen with understanding, has got rid of some of the āsavā. The d is an individual who has not reached the arūpa attainments, but, having seen with understanding, has got rid of some of the āsavā, and has thoroughly seen and considered the Teachings of the Tathāgata. The s is an individual who has not reached the arūpa attainments, but, having seen with understanding, has got rid of some of the āsavā, and whose saddhā in the Tathāgata is thoroughly established and well-rooted. All three are at least sotāpanna, but not yet arahat; and all three have some degree of samādhi, paññā, and saddhā, but each one emphasizes one of these three—the k puts samādhi first, the d puts paññā first, and the s puts saddhā first.
The Ekāyano ayam bhikkhave maggo sattānam visuddhiyā... of the Satipatthāna Sutta (M. 10: i,55; D. 22: ii,290) is, I regret to say, wrongly translated as 'This, monks, is the only way leading to the purification of beings...'; the proper translation (as pointed out by the late Ven. Ñānamoli Thera) is 'This way, monks, leads only to the purification of beings...', but the former translation is preferred by people who write about satipatthāna since it gives an added importance to their subject. Actually, the 'only way' leading to nibbāna is the noble eight-factored path (ariyo atthangiko maggo), of which satipatthāna is only one of the factors (the seventh).
As regards samādhi, the situation is this. As soon as a person reaches the first path (not the fruition, which may come much later—see CITTA) he gets the ariyapuggala's right view (sammāditthi), which is his paññā. And it is a characteristic of paññā that when one has it (as an ariyapuggala) one also has samādhi, viriya, saddhā, and sati.[a]
Now, one who has this paññā can, simply by developing his paññā, at the same time develop his samādhi; and when these have reached sufficient strength (more is required for each successive stage) the attainment of fruition takes place. Although the development of paññā is, of necessity, partly discursive (or intellectual), in the actual attainment of fruition (sotāpatti, etc.) the mind becomes steady (since samādhi has been automatically developed together with paññā, and the two now combine as equal partners—see M. 149: iii,289)—and there is direct intuition instead of discursive thinking. So in all attainment of fruition there is samādhi. But it is also possible for the ariyapuggala to develop his samādhi separately by means of ānāpānasati etc., and this is, in fact, the pleasantest way of advancing (for some people, however, it is difficult, and they have to grind away at vipassanā practice—i.e. development of paññā). In this way, a far greater degree of samādhi is developed than is actually necessary for the attainment of fruition; and so the k has arūpa attainments that he does not actually need to reach nibbāna.
The minimum strength of samādhi that is necessary for fruition is as follows: for arahattā and anāgāmitā, jhāna strength is needed (the first jhāna is enough)—see Mahāmālunkya Sutta, M. 64: i,432-37; for sakadāgāmitā and sotāpatti full jhāna is not needed—see A. IX,12: iv,378-82[b]—but it is necessary to have the samādhi nimitta (which comes long before jhāna)—see A. VI,68: iii,422-3. But the samādhi can be developed either separately beforehand (as explained above) or together with paññā, and presumably in cases where there is attainment simply on listening to the Buddha it is the latter. (I am aware that there has been a controversy about whether jhāna is or is not necessary for the attainment of sotāpatti, but, as so often in controversies, the disputants have gone to extremes. Those who assert that jhāna is necessary believe—rightly or wrongly—that their opponents are maintaining that no samādhi at all is necessary. But the fact of the matter is that some samādhi is necessary, but not full jhāna; and this may or may not, have been developed independently of paññā.) I am afraid (as you point out) that this question is rather complicated; but I think I have covered the ground. Let me know what is still not clear.
I shall sit on the letter from the French gentleman until I think of something to say to him. It seems that he wants me to publish a journal in French, but (i) my French is by no means equal to the task, and (ii) as the editor of a journal I should have to pass articles for publication that I see to be mistaken (nearly everything that is written these days is), and this I am not prepared to do at any price. (Let those who are 'objective' about their Dhamma, and are prepared to see two sides to every question—including nibbāna—occupy themselves with publishing contradictory articles.)
I have watched the men harvesting their paddy. When they come to a stalk that is still green they do not cut it at once but leave it to ripen. And if they find a stalk that has been cut lying by itself on the ground they bend down and pick it up and carefully put it with its companions where it belongs. In this way they make sure that nothing is lost. Now if only we took as much trouble over our thoughts what a harvest we should have!
[92.a] This fact is not understood by the puthujjana, who has no experience of such a phenomenon. Certainly he can get samādhi of a kind (by the practice of ānāpānasati, for example), but this is not the sammāsamādhi of the path (which he does not have). And similarly with viriya, saddhā, and sati. See BALA. [Back to text]
[92.b] This Sutta says that whereas the anāgāmī is samādhismim paripūrakārī, the sakadāgāmī is na paripūrakārī. (The former is one who 'fulfills samādhi', the latter is one who does not.) [Back to text]
[92.1] Mahāsalāyatanika Sutta: The Buddha discusses a man who knows and sees the eye, forms, eye-consciousness, eye-contact, and the pleasurable, painful, and neutral feelings that arise dependent upon eye-contact, as they really are (and mutatis mutandis for the other senses:
'That view as to what really is is his right view. That attitude as to what really is is his right attitude. That effort as to what really is is his right effort. That mindfulness as to what really is is his right mindfulness. That concentration as to what really is is his right concentration. And his bodily actions, his verbal actions, and his livelihood have already been well purified earlier. So this noble eightfold path comes to development and fulfillment in him. When he develops this noble eightfold path, the four foundations of mindfulness come to development and fulfillment in him. And the four right endeavours... the four bases of potency... the five faculties... the five powers... the seven factors of awakening come to development and fulfillment in him.
'These two things—peace and insight—are yoked harmoniously in him. By comprehension he fully understands those things that should be fully understood by comprehension. By abandoning he fully understands those things that should be fully understood by abandoning. By developing he fully understands those things that should be fully understood by developing. By realizing he fully understands those things that should be fully understood by realizing. And what, monks, should be fully understood by comprehension?...' [Back to text]
[92.2] A. VI,68: '"One not delighting in solitude could grasp the sign of the mind (cittassa nimittam)": such a state is not to be found. "One not grasping the sign of the mind could be fulfilled in right view": such a state is not to be found. "One not having fulfilled right view could be fulfilled in right concentration": such a state is not to be found. "One not having fulfilled right concentration could abandon the fetters": such a state is not to be found. "One not having abandoned the fetters could realize extinction": such a state is not to be found.' [Back to text]