Does Mahayana Buddhism discourage attaining enlightenment under the Gautama Buddha Sasana?

1. Non-Mahayana Theravada Buddhists^* aspire to become arahants. So, are they discouraged from performing wholesome karma to accumulate merit (puñña)? Probably not. Lay-following is not discouraged while there is still higher goal.

2. Mahayana distinctive feature is acceptance of all teachings of Buddha. So from Mahayana perspective non-Bohisattva teachings and practices are integral part of Dharma and possible for some types of personalities.

3. But, if person aspire to become budhisattva/buddha he probably should abstain from intent of leaving samsara to nirvana, but not from intent of reaching enlightenment (bodhi). He may wish to become enlightened bodhisattva, or even buddha.

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^* I assume that Mahayana Theravadin is possible, who don't deny Mahayana canon and/or aspire to become bodhisatta.

I'd like to answer because I don't think other (existing) answers have completely covered the topic.

Unfortunately I know very little about the subject! So I hope if you know better you may help to correct mistakes or suggest improvements in this answer.

Does Mahayana Buddhism discourage attaining enlightenment under the Gautama Buddha Sasana?

No -- Mahayana wants people to be enlightened.

Wikipedia:

According to the teachings of Mahāyāna traditions, "Mahāyāna" also refers to the path of the Bodhisattva seeking complete enlightenment for the benefit of all sentient beings, also called "Bodhisattvayāna", or the "Bodhisattva Vehicle". A bodhisattva who has accomplished this goal is called a samyaksaṃbuddha, or "fully enlightened Buddha". A samyaksaṃbuddha can establish the Dharma and lead disciples to enlightenment. Mahayana Buddhists teach that enlightenment can be attained in a single lifetime, and this can be accomplished even by a layperson.

In summary, enlightenment can be attained in one life (in this life), even by a layperson

I think there are various Mahayana doctrines which aren't the same as Theravada. If the Mahayana "Bodhisattvayāna" makes no sense to you, it might be because of some differences in the following doctrines (and so, if I'm right and if you're interested, it might make sense to ask more about these aspects of Mahayana doctrine).

• Some forms of Mahayana teach "sudden enlightenment" -- see Subitism -- not all schools, though, I think it's more a feature of some Chan and Zen schools than Tibetan. I mention it as one example of a doctrine that enlightenment is possible.
• IMO it might be better for everyone if the world contains Bodhisattvas than if it doesn't. If you say it's true that there's a conflict between being an Arhat and being a Bodhisattva, some Mahayana doctrines teach it's better to be a Bodhisattva -- see Arhat in Mahayana Buddhism
• Mahayana might also have a different definition of "enlightenment" or the enlightened state, enlightened views, enlightened behaviour, and so on. In particular, Nirvana is not the ultimate, best, or only form of enlightenment -- see Nirvana and Mahayana
• Mahayana might also have a different doctrine of what happens after death. I think that parinibbana in Theravada is some kind of permanent extinction or dissolution -- whereas in Mahayana the consciousness (or something like that) of the enlightened being continues, and exist in some kind of Pure land.
• This doctrine applies to Arhats too -- they too continue to exist after parinibbana in a pure land, in meditative equipoise (which is also known as samatha).
• Buddhas and enlightened beings can return to this realm -- perhaps, I don't know, not in quite the same way as normal rebirth.

In summary:

• Enlightenment is taught as a good (even a highest) aspiration, and as feasible not impossible
• The Bodhisattvayāna aspiration might seem illogical given the Theravada definitions, but Mahayana has several distinct doctrines e.g. about what enlightenment is, what parinibbana is, whether an enlightened being can remanifest, so it's not illogical according to those doctrines.

I might add that Mahayana includes relying on or benefiting from the Buddha. That's not part of the question, but I wanted to mention it because it's important.

I'd like to see a canonical(Mahayana) reference to the view that enlightened beings continue after death.

Here are some Wikipedia references which suggest that's so.

• Pure land

  A pure land is the celestial realm or pure abode of a buddha or bodhisattva in Mahayana Buddhism. The term "pure land" is particular to East Asian Buddhism (Chinese: 淨土, Jìngtǔ) and related traditions; in Sanskrit the equivalent concept is called a "buddha-field" (Sanskrit buddhakṣetra).

  In the Mahayana sutras, there are many pure lands. Bodhisattvas such as Avalokiteśvara and Manjusri would obtain pure lands after they attained buddhahood.

  The Śuddhāvāsa (Pāli: Suddhāvāsa; Tib: gnas gtsang.ma) worlds, or "Pure Abodes", are distinct from the other worlds of the Rūpadhātu in that they do not house beings who have been born there through ordinary merit or meditative attainments, but only those Anāgāmins ("Non-returners") who are already on the path to Arhat-hood and who will attain enlightenment directly from the Śuddhāvāsa worlds without being reborn in a lower plane (Anāgāmins can also be born on lower planes). Every Śuddhāvāsa deva is therefore a protector of Buddhism. (Brahma Sahampati, who appealed to the newly enlightened Buddha to teach, was an Anagami from a previous Buddha). Because a Śuddhāvāsa deva will never be reborn outside the Śuddhāvāsa worlds, no Bodhisattva is ever born in these worlds, as a Bodhisattva must ultimately be reborn as a human being through their 'compassion' (Sanskrit: Karuṇā) and bodhisattva vows.

• Saṃbhogakāya

  The Sambhogakaya is a "subtle body of limitless form". Both "celestial" Buddhas such as Bhaisajyaguru and Amitābha, as well as advanced bodhisattvas such as Avalokiteśvara and Manjusri can appear in an "enjoyment-body."[citation needed] A Buddha can appear in an "enjoyment-body" to teach bodhisattvas through visionary experiences. Those Buddhas and Bodhisattvas manifest themselves in their specific pure lands. These worlds are created for the benefits of others. In those lands it is easy to hear and practice the Dharma. A person can be reborn in such a pure land by "the transfer of some of the huge stock of 'merit' of a Land's presiding Buddha, stimulated by devout prayer. One of the places where the Sambhogakāya body appears is the extra-cosmic realm or pure land called Akaniṣṭha. This is one of the highest realms of the Śuddhāvāsa devas. Absolutely seen, only the Dharmakāya is real; the Sambhogakāya and Nirmanakaya are "provisional ways of talking about and apprehending it".

• Buddhology -- Eternal Buddha

  An important doctrine that flourished during the middle period of the unfolding of the Mahayana - and is still important today amongst certain Mahayana schools of Buddhism - is that of the Buddha's immortality and eternity. The idea of an eternal Buddha is a notion popularly associated with the Mahayana scripture, the Lotus Sutra, which was written down about 500 years after Shakyamuni`s preaching of it.. The Lotus Sutra has the Buddha indicating that he became awakened countless, immeasurable, inconceivable trillions of aeons ("kalpas") ago and that his lifetime is "forever existing and immortal". The sutra itself, however, does not directly employ the phrase "eternal Buddha"; yet similar notions are found in other Mahayana scriptures, notably the Mahaparinirvana Sutra, which presents the Buddha as the ultimately real, eternal ("nitya"/ "śāśvata"), unchanging, blissful, pure Self (Atman) who, as the Dharmakaya, knows of no beginning or end. The notion of an eternal Buddha perhaps finds resonance with the earlier idea of eternal Dharma/Nirvana, of which the Buddha is said to be an embodiment.

  While Theravada Buddhism holds back from stating that the Buddha is eternal and emphasises all-round impermanence, some expressions of Mahayana Buddhism, however, regard such an understanding as incomplete. The Tathagatagarbha sutras provide an allegedly culminational doctrine of a pure Selfhood (the eternal yet ungraspable hypostasis of the Buddha) which no longer generates karma and which subsists eternally in the realm of Nirvana, from which sphere help to suffering worldly beings can be sent forth in the forms of various transitory physical Buddhas ("nirmānakāyas"). While the bodies of these corporeal Buddhas are subject to disease, decline and death - like all impermanent things - the salvational Tathagata or Dharmakaya behind them is forever free from impairment, impermanence and mortality. It is this transcendent yet immanent Dharmakaya-Buddha which is taught in certain major Mahayana sutras to be immutable and eternal and is intimately linked with Dharma itself. According to the Mahayana Mahaparinirvana Sutra, worldly beings fail to see this eternality of the Buddha and his Dharma. The Buddha declares in that latter Mahayana sutra, which presents itself as the last and most definitive of all sutras: "I say that those who do not know that the Tathagata [Buddha] is eternal are the foremost of the congenitally blind."

This might be relevant too, if only as a description of a relevant or related practice:

• Deity yoga

  Deity yoga (Tibetan: lha'i rnal 'byor; Sanskrit: Devata-yoga) is a practice of Vajrayana Buddhism involving identification with a chosen deity through visualisations and rituals, and the realisation of emptiness.

  The purpose of Deity yoga is to bring the meditator to the realization that the yidam or meditation deity and the practitioner are in essence the same, that they are non-dual (advaya). According to John Powers. "Deity yoga is a technique for becoming progressively more familiar with the thoughts and deeds of a buddha, until the state of buddhahood is actualized through repeated practice."

  According to Gyatrul Rinpoche, the point of this practice is to "understand your buddha nature, which is the very essence of your being" and is "intrinsically present" in all beings.

Here's a description of Bodhicitta (the motive or intention or state of mind). I think this does imply (accepting or aspiring to) rebirths, but doesn't imply a desire (nor need) to remain unenlightened:

• Bodhicitta

  In Buddhism, bodhicitta, "enlightenment-mind", is the mind that strives toward awakening, empathy, and compassion for the benefit of all sentient beings.

  Bodhicitta is a spontaneous wish to attain enlightenment motivated by great compassion for all sentient beings, accompanied by a falling away of the attachment to the illusion of an inherently existing self.

  The mind of great compassion and bodhicitta motivates one to attain enlightenment Buddhahood, as quickly as possible and benefit infinite sentient beings through their emanations and other skillful means. Bodhicitta is a felt need to replace others' suffering with bliss. Since the ultimate end of suffering is nirvana, bodhicitta necessarily involves a motivation to help others to awaken (to find bodhi).

  A person who has a spontaneous realization or motivation of bodhicitta is called a bodhisattva.

And here are quotes from The Jewel Ornament Of Liberation which describe the attainments of the non-Mahayana (non-Bodhisattva) families as not final -- and, in contrast, its description of the Mahayana family -- and finally its describing Buddhahood as the aspiration:

BUDDHA-NATURE

We need to attain unsurpassable enlightenment by freeing ourselves from the confused state of samsara. But, is it possible for inferior persons like ourselves to achieve enlightenment even if we make the effort? Why wouldn’t we attain enlightenment if we made the effort! All sentient beings, including ourselves, already possess the primary cause for enlightenment, the Essence of the Well-gone One.

HEARER FAMILY and SOLITARY REALIZER FAMILY

The family of Hearers consists of those who fear samsara and yearn to achieve nirvana, but who have little compassion. It has been said:

One who is afraid upon seeing the suffering of samsara
And yearns to achieve nirvana
But has little interest in benefitting sentient beings—
These three are the marks of the Hearer family

The Solitary Realizer family includes those who possess the above three attributes and in addition are arrogant, keep their masters’ identities secret, and prefer to stay in solitary places. It has been said:

Fear at the thought of samsara, yearning for nirvana,
Little compassion, arrogance,
Secretive about their teachers, and enjoying solitude—
A wise one should understand that these are the marks of the Solitary Realizer family

So these two families, the Hearers and the Solitary Realizers, engage in their respective vehicles and even though they achieve the results of their practices, these results are not the final nirvana. How do they abide when they achieve their fruits? They maintain unafflicted states of meditative concentration, but those states are based on the psychic imprint of ignorance. Since their meditative concentrations are unafflicted, they believe that they have achieved nirvana and remain that way.

If their states are not the final nirvana, then one might argue that the Buddha should not have taught these two paths. Is there a reason the Buddha should teach such paths? Yes. For example, suppose great merchants from this Jambudvipa are traveling the ocean searching for jewels. After many months at sea, in some desolate place, they become completely tired and exhausted and think, “There is no way to get the jewels now”. When they feel discouraged and prepare to turn back, the merchant captain manifests a huge island through his miracle power and lets all his followers rest there. After a few days, when they are fully rested and relaxed, the captain says, “We have not achieved our goal. Now we should go farther to get our jewels.”

Similarly, sentient beings without courage are frightened when they hear about the Buddha’s wisdom. They believe attaining Buddhahood is a great hardship, and think, “I have no ability to do this.” There are other people who are not interested in entering the path, or who enter the path but turn back. To counter these problems, Buddha presented these two paths, and allows them to rest in these states.

As said in the White Lotus of Sublime Dharma Sutra:

Likewise, all the Hearers
Think that they achieved nirvana,
But they have not achieved the final nirvana
Revealed by the Buddha
They are only resting

When these Hearers and Solitary Realizers are well rested in those states, Buddha understands this and encourages them to attain Buddhahood. How does Buddha encourage them? He awakens them through his body, speech, and wisdom mind. “Through wisdom mind” means that light radiates through the Buddha’s wisdom and touches the mental bodies of the Hearers and Solitary Realizers. As soon as the light reaches them, they arise from their unafflicted meditations. Then the Buddha appears physically in front of them. With his speech he says:

O you monks
You have not finished your deeds, you have not finished all that you are supposed to do
Your experience of nirvana is not the final nirvana
Now all you monks have to work toward enlightenment
You should attain the realization of the Buddha

From the White Lotus of Sublime Dharma Sutra, in verse form:

You, monks, today I declare
You have not achieved the final nirvana
In order to achieve the primordial wisdom of the Omniscient One,
You must cultivate great perseverance
Through that, you will achieve the wisdom of the Omniscient One

Being motivated by the Buddha in this way, these Hearers and Solitary Realizers cultivate bodhicitta. They practice the bodhisattva’s path for many limitless kalpas and eventually achieve enlightenment. The Gone to Lanka Sutra relates the same thing. Also, the White Lotus of Sublime Dharma Sutra says:

These Hearers have not achieved nirvana
By thoroughly practicing the bodhisattva’s path,
They will achieve Buddhahood

MAHAYANA FAMILY

The Hearer and Solitary Realizer families are inferior by virtue of the fact that they fully purify their families by dispelling only the obscuration of afflicting emotions. The Mahayana is superior because it fully purifies its family by dispelling two obscurations—afflicting emotions and the subtle obscurations to enlightenment. Therefore, the Mahayana family is superior and unsurpassed.

[...]

The marks of this family are the signs which indicate the bodhisattva family.

The Ten Noble Bhumis Sutra says
The family of wise bodhisattvas
Can be recognized by its signs
Just as fire is known by its smoke
And water is known by water birds

In that case, what kinds of marks are there? Their bodies and speech are naturally gentle without dependence on a remedy. Their minds are less deceitful, and have loving-kindness and clarity toward sentient beings. Thus, the Ten Noble Bhumis Sutra says:

No harshness or arrogance,
Avoiding all deceit and cunning,
Having a clear, lovmg attitude toward all sentient beings—
This is a bodhisattva

In other words, in whatever preparatory actions a bodhisattva undertakes, he always cultivates compassion for all sentient beings, has a great inclination toward the Mahayana teachings, has no hesitation to endure hardships, and perfectly performs the root virtue of the perfections. Thus, the Ornament of Mahayana Sutra says:

Developing compassion at the preparation stage,
Devoted interest, patience,
Perfectly performing the virtues—
These are the signs of the Mahayana family

Thus, of these five families, those who are the Mahayana family are very close to the cause of enlightenment. The Hearer and Solitary Realizer families will eventually lead to Buddhahood, but the cause is farther away and it will take a long time. In the indefinite family, some are close and some will take a long time. The disconnected family is known by Buddha to wander in samsara for a long time, but this does not mean that they absolutely will not attain Buddhahood. They can attain Buddhahood, but it will take a very long time. Therefore, since all sentient beings belong to one of these families, all sentient beings are of the Buddha-nature. Thus, by the above three reasons, it has been demonstrated that all sentient beings have the Buddha-nature. Furthermore, consider these examples: silver abiding in its ore, oil abiding in a mustard seed, and butter abiding in milk. From silver ore, we can produce silver, from mustard seed, we can produce oil, and from milk, we can produce butter. Likewise, sentient beings can become Buddhas.

I hope that helps to clarify the Mahayana motivation. In any case I think that motivation isn't to discourage attaining enlightenment, but is instead to try to practice, to learn, to teach enlightenment (in this sasana).

"So, are Mahayana Buddhists discouraged from attaining enlightenment within the Gautama Buddha Sasana?"

Emphatically no! This is a misconception.

If the answer to the first question is 'no', any links to Mahayana specific texts which encourage one to attain Nibbana within this Sasana would be appreciated.

How about a Bodhisattva vow? This is the auxiliary vow #14:

To abandon: Believing and saying that followers of the Mahayana should remain in cyclic existence and not try to attain liberation from afflictions.

It says in the Mahayana texts that bodhisattvas give up enlightenment and remain in samsara or cyclic existence for the benefit of others. And so there is the danger that you misunderstand this and think, “Oh, bodhisattvas don’t try and get enlightened. They just stay in samsara. Because they don’t try and get enlightened, then they don’t apply the antidotes to the afflictions. They don’t purify their karma because they’re staying in samsara to benefit others.

If you think like that, that’s a misconception. That’s what this precept is getting at. Although it says that bodhisattvas remain in cyclic existence to benefit others, what that means is, a bodhisattva’s compassion for others is so strong that if it would be of ultimate benefit for sentient beings for a bodhisattva not to be enlightened, then the bodhisattva would happily give up even their own enlightenment because they’re so committed to serving sentient beings. But it clearly isn’t for the benefit of sentient beings for bodhisattvas not to be enlightened. Because a bodhisattva has this much ability to help others and the Buddha has this much ability to help others, so bodhisattvas are going to try really hard to get enlightened. They’re definitely going to apply the antidotes to the afflictions and purify their karma. And while they’re on the bodhisattva path, they’re still going to continue to come back to our world in order to benefit sentient beings.

The answer given above that plays into this misconception is erroneous and does not come from a self-identified Mahayana practitioner. It simply isn't the case that the Mahayana properly understood instructs Bodhisattvas to keep their afflictions or remain unenlightened in order to help others. That would be nonsensical and is thus not the case.

Objection! Hey, what about this verse from Atisha's Lamp for the Path to Enlightenment (page 125):

29. “I shall not be eager to reach
    Enlightenment in the quickest way,
    But shall stay behind till the very end,
    For the sake of a single being.

As His Holiness explains in the commentary to the text, this verse was taken from Shantideva's famous Bodhicaryavatara. A Bodhisattva is someone who vows to achieve enlightenment not for themselves, but rather motivated purely with the altruistic wish to help others. This verse reflects how someone aspiring to become a Bodhisattva should train their mind to achieve this pure altruistic motivation. It shows that a Bodhisattva is not someone who wishes to reach liberation in the quickest way possible for themselves alone. Although it might appear contradictory to the vow above, it is not in actual fact contradictory.

See this:

A commonly repeated misconception in Western literature is that bodhisattvas delay their own liberation. This confusion is based on a misreading of several different scriptural concepts and narratives. One of these is the Tibetan teaching on three types of motivation for generating bodhicitta. According to Patrul Rinpoche's 19th century Words of My Perfect Teacher (Kun bzang bla ma'i gzhal lung), a bodhisattva might be motivated in one of three ways. They are:

king-like bodhicitta - to aspire to become a buddha first in order to then help sentient beings
boatman-like bodhicitta - to aspire to become a buddha at the same time as other sentient beings
shepherd-like bodhicitta - to aspire to become a buddha only after all other sentient beings have done so

These three are not types of people, but rather types of motivation. According to Patrul Rinpoche, the third quality of intention is most noble though the mode by which buddhahood actually occurs is the first; that is, it is only possible to teach others the path to enlightenment once one has attained enlightenment oneself.

And more from Venerable Thubten Chodron here and here saying essentially the same thing:

The first one, the shepherd-like bodhisattva: when the shepherd goes, the sheep go in front. This is the bodhisattva that says, “Ok, I’m giving up my own enlightenment, and everybody else gets enlightened, then I get enlightened.” This seems to contradict what I said yesterday.

Then there’s the oarsman-type of bodhisattva, because he’s in the same vehicle so they arrive at enlightenment at the same time.

And then there’s the king-like bodhisattva: the king usually goes first, then everybody else follows in the entourage. That bodhisattva attains enlightenment first and then leads everybody else there.

They give these three examples and they say that actually the king-like bodhisattva’s the one of the highest faculties, because they realized that actually it’s more important to attain enlightenment for the benefit of others then to stay in samsara and not be able to help anybody as well as you could if you were already a buddha. They said that actually all bodhisattvas eventually get around to being king-like bodhisattvas and attain enlightenment for the benefit of sentient beings.

So the correct way to think about verses like the above about not being "eager to reach Enlightenment in the quickest way" for the sake of oneself is as a mind training for generating this shepherd-like pure altruistic motivation whereas in actual fact a Bodhisattva with high faculties will realize that to accomplish the goal of this pure altruistic motivation requires enlightenment and liberation in the quickest way possible!

To see just how wide of an agreement there is on this see also this quote from His Holiness the Dalai Lama:

Question: When a practitioner of the Great Vehicle vows not to enter into nirvana until all beings are liberated, how is it possible to fulfill this vow?

Answer: Three modes of generating an altruistic intention to become enlightened are described--like a king, like a boatman, and like a shepherd. In the first, that like a king, one first seeks to attain a high state after which help can be given to others. In the second, like a boatman, one seeks to cross the river of suffering together with others. In the third, like a shepherd, one seeks to relieve the flock of suffering beings from pain first, oneself following afterward. These are indications of the style of the altruistic motivation for becoming enlightened; in actual fact, there is no way that a Bodhisattva either would want to or could delay achieving full enlightenment. As much as the motivation to help others increases, so much closer does one approach Buddhahood.

Emphasis mine.

Now, there seems to be one significant area of disagreement between the Sanskit tradition and the Pali tradition (notice I didn't use Mahayana and Theravada on purpose) when it comes to the understanding of the attainments of the three vehicles. This is in Buddhism: One Teacher, Many Traditions:

Some Buddhists say at the time of nirvana without remainder, the continuum of consciousness of the person ceases although nirvana without remainder exists. However, other Buddhists assert that all sentient beings will eventually attain buddhahood and the continuum of consciousness exists even after arhats pass away. At that time, arhats have a mental body and reside in a pure land, where they remain in meditative equipoise on emptiness. At the appropriate time, the Buddha arouses them from their meditative equipoise and causes them to enter the bodhisattva path and attain a buddha's awakening.

So while it is clear that the Sanskrit and Pali traditions differ in this respect, it is not at all the case that the Sanskrit or Mahayana practitioners in general discourage beings from attaining enlightenment or liberation with the Gautama Buddha Sasana.

Re: "Mahayana Buddhists aspire to become Buddhas themselves in the future" -- if I can speak for "Mahayana Buddhists", they say that in order to correctly follow the teaching of Gautama Buddha, one must fully understand what Gautama Buddha meant when he spoke his teaching, which means one must clearly see what Gautama Buddha saw under the Bodhi tree (if not all infinite depth, at least its main essence). When one attains the same vision that Gautama Buddha attained, and completely realizes in practice the same practice that Gautama Buddha realized, one effectively becomes equivalent to a buddha, and for all practical purposes we can call such fully realized student "a buddha". It is in this sense that "Mahayana Buddhists aspire to become Buddhas themselves in the future".

"or want to become followers of a future Buddha like Buddha Maitreya" -- if next Buddha comes here tomorrow, wouldn't you want to become a follower and get the teaching from the first hands?

"So, are Mahayana Buddhists discouraged from attaining enlightenment within the Gautama Buddha Sasana?" -- this is an incorrect conclusion you drew from an incorrect understanding of two assumptions above. Mahayana Buddhists do not reject Gautama Buddha dispensation, quite the opposite, they aspire to be the best students of Gautama Buddha, to the point of equating their teacher in vision and realization one day; they also put the true spirit of the teaching above the letter of the teaching, which is why they prefer live tradition whenever possible.