Why did Buddha use the 'Raft Simile'?

The sutta is about not arguing about the Dhamma rather than not practising the Dhamma.

Here, bhikkhus, some misguided men learn the Dhamma—discourses, stanzas, expositions, verses, exclamations, sayings, birth stories, marvels, and answers to questions—but having learned the Dhamma, they do not examine the meaning of those teachings with wisdom. Not examining the meaning of those teachings with wisdom, they do not gain a reflective acceptance of them. Instead they learn the Dhamma only for the sake of criticising others and for winning in debates, and they do not experience the good for the sake of which they learned the Dhamma. Those teachings, being wrongly grasped by them, conduce to their harm and suffering for a long time. Why is that? Because of the wrong grasp of those teachings

Suppose a man needing a snake, seeking a snake, wandering in search of a snake, saw a large snake and grasped its coils or its tail. It would turn back on him and bite his hand or his arm or one of his limbs, and because of that he would come to death or deadly suffering. Why is that? Because of his wrong grasp of the snake. So too, here some misguided men learn the Dhamma…Why is that? Because of the wrong grasp of those teachings.

Having crossed and arrived at the other shore, he thinks: 'This raft, indeed, has been very helpful to me. Carried by it, laboring with hands and feet, I got safely across to the other shore. Should I not lift this raft on my head or put it on my shoulders, and go where I like?'

No, venerable sir.

'Suppose I were to haul it onto the dry land or set it adrift in the water, and then go wherever I want.’ Now, bhikkhus, it is by so doing that that man would be doing what should be done with that raft.

So the above teaching does not say to destroy the raft. Nor does it say to carry the raft on your back as a burden (via arguments or trying to convert the unconvertible). It simply says to set it adrift or haul it onto dry land (for others to use).

You need to do good things, good because they are means to an end, are supports for crossing. Having reached the end these good things are still a means to an end but that for another person and not for this good person who by means of these good things has gone to the end and crossed over.

The Translator's Introduction by Ven. Thanissaro suggests an explanation.

The first section of the discourse, leading up to the simile of the water-snake, focuses on the danger of misapprehending the Dhamma in general, and particularly the teachings on sensuality. The discourse doesn't explain how the offending monk, Arittha, formulated his misapprehension of the Dhamma, but the Commentary suggests a plausible scenario:

"Here the monk... having gone into seclusion, reasons as follows: 'There are people living the household life, enjoying the five pleasures of the senses, who are stream-winners, once-returners, and non-returners. As for monks, they see pleasurable forms cognizable via the eye, hear... smell... taste... feel (pleasurable) tactile sensations cognizable via the body. They use soft carpets and clothing. All this is proper. Then why shouldn't the sight, sound, smell, taste, and feel of a woman be proper? They too are proper!' Thus... comparing a mustard seed with Mount Sineru, he gives rise to the pernicious viewpoint, 'Why did the Blessed One — binding the ocean, as it were, with great effort — formulate the first parajika training rule (against sexual intercourse)? There is nothing wrong with that act.'"

Regardless of how Arittha actually arrived at his position, the Commentary's suggestion makes an important point: that just because an idea can be logically inferred from the Dhamma does not mean that the idea is valid or useful. The Buddha himself makes the same point in AN 2.25:

"Monks, these two slander the Tathagata. Which two? He who explains a discourse whose meaning needs to be inferred as one whose meaning has already been fully drawn out. And he who explains a discourse whose meaning has already been fully drawn out as one whose meaning needs to be inferred..."

Having established this point, the discourse illustrates it with the simile of the water-snake, which in turn is an introduction to the simile of the raft. It is important to underline the connection between these two similes, for it is often missed. Many a casual reader has concluded from the simile of the raft simply that the Dhamma is to be let go. In fact, one major Mahayana text — the Diamond Sutra — interprets the raft simile as meaning that one has to let go of the raft in order to cross the river. However, the simile of the water-snake makes the point that the Dhamma has to be grasped; the trick lies in grasping it properly. When this point is then applied to the raft simile, the implication is clear: One has to hold onto the raft properly in order to cross the river. Only when one has reached the safety of the further shore can one let go.

Part of the sutta is about not arguing (e.g. having grasped the Dhamma wrongly people then argue about it -- the watersnake simile).

I think the raft simile is slightly different and is about taking logic or an analogy too far. There's an example of that -- carrying logic too far and so arriving at a wrong conclusion -- in the Commentary which the translator quotes above.

If I can try to clarify my point by inventing an even more obvious or more absurd example, that might be, "Because Dhamma is 'like a raft' then I can literally jump into this river without getting wet and drowning" -- but no, that isn't true, that would be taking the analogy too far.

So the Buddha uses words and analogies to explain what he wants to explain. Don't take that message too far, wrongly adding logic to use it as a proof of something else, even something contrary.

I expect there are many possible mistakes of logic or interpretation. One of them is described in the parable of the blind men and the elephant in Ud 6.4:

Those blind people who had been shown the head of the elephant replied, 'An elephant, your majesty, is just like a water jar.' Those blind people who had been shown the ear of the elephant replied. "An elephant, your majesty, is just like a winnowing basket.' Those blind people who had been shown the tusk of the elephant replied, 'An elephant, your majesty, is just like a plowshare.' Those blind people who had been shown the trunk replied, 'An elephant, your majesty, is just like a plow pole.' Those blind people who had been shown the body replied, 'An elephant, your majesty, is just like a storeroom.' Those blind people who had been shown the foot replied, 'An elephant, your majesty, is just like a post.' Those blind people who had been shown the hindquarters replied, 'An elephant, your majesty, is just like a mortar.' Those blind people who had been shown the tail replied, 'An elephant, your majesty, is just like a pestle.' Those blind people who had been shown the tuft at the end of the tail replied, 'An elephant, your majesty, is just like a broom.'

"Saying 'An elephant is like this, an elephant is not like that! An elephant is not like this, an elephant is like that!' they fought each other with their fists.

I think it's good to ask, knowing what we know, whether it's true that an elephant is like a jar, like a basket, like a plowshare, etc.

I think the answer is that it both is like that and isn't like that.

This parable too is about ("sectarians") arguing, but it's also about incorrectly grasping or attaching to a specific view.

The one who dwells in the Dhamma according to the sutta below, is the one who uses it as a raft to cross over.

The one who is keen on the Dhamma's study, description, recitation, pondering but does not cultivate inner tranquility of awareness, does not dwell in the Dhamma. This person is attached to the raft and is not using it to cross over.

However, the one who studies and ponders the Dhamma, and also cultivates inner tranquility of awareness, dwells in the Dhamma. This person uses the Dhamma as a raft to cross over.

From Dhammaviharin Sutta (AN 5.73):

Then a certain monk went to the Blessed One and, on arrival, having bowed down to him, sat to one side. As he was sitting there he said to the Blessed One, "'One who dwells in the Dhamma, one who dwells in the Dhamma': thus it is said, lord. To what extent is a bhikkhu one who dwells in the Dhamma?"

"Monk, there is the case where a monk studies the Dhamma: dialogues, narratives of mixed prose and verse, explanations, verses, spontaneous exclamations, quotations, birth stories, amazing events, question & answer sessions. He spends the day in Dhamma-study. He neglects seclusion. He doesn't commit himself to internal tranquillity of awareness. This is called a monk who is keen on study, not one who dwells in the Dhamma.

"Then there is the case where a monk takes the Dhamma as he has heard & studied it and teaches it in full detail to others. He spends the day in Dhamma-description. He neglects seclusion. He doesn't commit himself to internal tranquillity of awareness. This is called a monk who is keen on description, not one who dwells in the Dhamma.

"Then there is the case where a monk takes the Dhamma as he has heard & studied it and recites it in full detail. He spends the day in Dhamma-recitation. He neglects seclusion. He doesn't commit himself to internal tranquillity of awareness. This is called a monk who is keen on recitation, not one who dwells in the Dhamma.

"Then there is the case where a monk takes the Dhamma as he has heard & studied it and thinks about it, evaluates it, and examines it with his intellect. He spends the day in Dhamma-thinking. He neglects seclusion. He doesn't commit himself to internal tranquillity of awareness. This is called a monk who is keen on thinking, not one who dwells in the Dhamma.

"Then there is the case where a monk studies the Dhamma: dialogues, narratives of mixed prose and verse, explanations, verses, spontaneous exclamations, quotations, birth stories, amazing events, question & answer sessions. He doesn't spend the day in Dhamma-study. He doesn't neglect seclusion. He commits himself to internal tranquillity of awareness. This is called a monk who dwells in the Dhamma.

"Now, monk, I have taught you the person who is keen on study, the one who is keen on description, the one who is keen on recitation, the one who is keen on thinking, and the one who dwells in the Dhamma. Whatever a teacher should do — seeking the welfare of his disciples, out of sympathy for them — that have I done for you. Over there are the roots of trees; over there, empty dwellings. Practice jhana, monk. Don't be heedless. Don't later fall into regret. This is our message to you."

The teachings contain advice for unenlightened persons for e.g. to think "I am the owner of my kamma, the heir of my kamma; I have kamma as my origin, kamma as my relative, kamma as my resort; I will be the heir of whatever kamma, good or bad, that I do" from AN 5.57. By contemplating this, they will abandon their evil deeds.

This helps them on the path to enlightenment. But to an enlightened person, this advice is not useful, as they have completely abandoned self-view, conceit, craving, clinging and the three poisons of greed, aversion and delusion. The enlightened person needs to eventually abandon the "I am the owner of my kamma" view too. It was useful on the path, but no longer useful after crossing over. This is an example of how even the teachings are eventually abandoned upon crossing over.

This Pali Canon parable is one of the two most popular images among Mahayana students (the other one being the parable of toys used to lure children out of the burning house).

The other shore is Nirvana and the raft is the concepts (of Dharma). The concepts are used to get across, but the final destination is beyond concepts. Rafts don't move on dry land, sun rays have nowhere to fall if there's no ground. Concepts don't hold in Emptiness, they have nothing to hang on.

The whole point of Buddha's teaching is liberation of mind. The entire appearance of samsara with all its problems and sufferings is a giant self-perpetuating complex of concepts. Our problems are concepts in the space of relative definitions. To be a master of concepts rather than victim of, is what the practice is all about. Being a master of concepts one can create and destroy concepts as needed, without being bounded by them.

Unbounded, vast, limitless, open - is the other shore. The raft of Dharma is a vehicle, not the destination.