Why can an arhat not have the thought, "I have attained the fruit of arhatship"?

Original text: 须菩提。于意如何。阿罗汉能作是念。我得阿罗汉道不。不也。世尊。何以故。实无有法。名阿罗汉。世尊。若阿罗汉作是念。我得阿罗汉道。即为著我人众生寿者。

The Buddha said to Subhūti: What do you think of this matter? Can an arhat have the thought, "I have attained the arhat fruit"? Subhūti replied: An arhat cannot have such a thought, World-Honored One. Why is this said? Because there truly is no dharma that can be named "arhat." World-Honored One, if an arhat thinks in his mind: "I have realized the arhat fruit," then he has grasped the mark of self, the mark of person, the mark of sentient being, and the mark of life span, and he would no longer be an arhat.

Anyone who has the thought in mind, "I have accomplished such and such," believing there truly is a self who has accomplished such and such, has grasped the mark of self, and the other three marks will then appear accordingly. The same is true for an arhat: if he believes he has realized the arhat fruit, there is the mark of self in his mind, and then the mark of person, the mark of sentient being, and the mark of life span will all clearly exist as well; such a person is not an arhat. In this world there truly is no dharma called "arhat." The five aggregates composed of an arhat's material body and conscious mind are subject to arising, ceasing, change, and illusion; they are not truly existing dharmas and cannot be called an arhat. The arhat fruit is merely a state and a realm; there is no substantial fruit to be obtained or seen. The realization of the arhat fruit is itself an illusory dharma of arising, ceasing, and change, not a truly existing dharma. If it were a truly existing dharma, it would exist eternally, and one would eternally realize the arhat fruit without needing to cultivate.

Therefore an arhat has no such thought as "I have realized the arhat fruit." After realizing the arhat fruit, his mind is empty and tranquil, without even a trace of the four marks; walking in the human world, he is like an empty shell, without any conflicts or disputes. Ordinary beings are just the opposite: due to the mischief of the view of self, the four marks abound, and they are constantly mired in afflictions and disputes. The heavier a person's view of self, the heavier his mark of self, the less pure his mind, the heavier his afflictions, and the more conflicts and disputes he has; conversely, the purer he is, the fewer conflicts and disputes he has.

From the first fruit to the fourth fruit, the noble ones of the Small Vehicle all lack the four marks; Mahāyāna bodhisattvas should all the more not grasp the four marks. Likewise, they would not have thoughts such as "I have seen the mind," "I have seen the nature," "I have become a bodhisattva of the ten stations, the ten practices, or the ten dedications," nor would they go around proclaiming, "I am a bodhisattva of the first bhūmi," "I am a bodhisattva of the second bhūmi," "I am a bodhisattva of the third or fourth bhūmi, or even the eighth bhūmi," and even less would they proclaim everywhere, "I am so-and-so, a sage who has come again," "I am so-and-so, a Buddha who has come again." The bodhisattva's mind is purer than that of the śrāvakas, for after all they have realized the emptiness of both the Great and Small Vehicles. Śrāvakas have only realized the emptiness of worldly marks; they have not realized the self-natured pure mind and do not know why the worldly empty marks and empty dharmas are empty, so their realization of emptiness is not yet pure enough. Bodhisattvas would not have these impure, unreasonable thoughts, nor would they engage in grand publicity to win over crowds in this way. A person of true realization has a mind that is empty and pure, not grasping any dharma mark, and is truly worthy of our respect and emulation.