Twelve Links of Dependent Origination

When a mind (vijñāna) conditioned (saṃskāra) by ignorance (avidyā) conceives (nāmarūpa) an impression (sparśa) through the six senses (ṣaḍāyatana) that feels (vedanā) pleasant/unpleasant, then it craves (tṛṣṇā) for its continuation/discontinuation, attempts to keep (upādāna) and identify (bhava) with it, but with its birth (jāti) comes its decay and demise (jarāmaraṇa).

When one is ignorant about how suffering arises and ceases, then one concocts/fabricates physical, verbal, and mental activities to perform, and that results in a mindset/attitude (consciousness) that regulates one's bodily and mental functions, thus colouring one's senses, so when there is an impression (contact) and a related quality (feeling), then necessarily one enjoys and delights in it (craving), therefore wants to hang on to it (clinging), and that turns into an identity (becoming), so it defines one's whole being (birth), but eventually, like everything else, it'll fall apart and thus cause pain.

The twelve links are present at each instance of suffering ignorantly. It's not that when there is one link present, like feeling, then the others are missing. When one feels something pleasant (note that already that single feeling exists in a compounded way within a network of conditions), then there had to be a contact with something through the six sense gates, and that thing is recognised as a particular form with a particular name, and one has an opinion (mindset) of that thing that is primarily driven by an intention, and that motivation can exist because of not knowing any better. Because of the presence of the preconditions it is inevitable that the feeling of something pleasant is met with liking it, the need to hold it, and thus defining one's whole experience of the world, what in turn gives rise to a fixed set of particular behaviour and mentality that will necessarily deteriorate and decease.
Let's take an apple juice as an example for a pleasant object. To recognise it as such one needs to come in contact with it (seeing/tasting/imagining), and that contact to be meaningful one needs a couple of preconditions, like knowing what an apple juice is and an opinion of it whether one likes it or not. Since one recognises the apple juice as something desirable, it is a pleasant object. With the recognition of the tasty juice comes the thirst for it, the thirst develops into the need to have it, that grows into the thought of being the one who delightedly experiences drinking it. With those present arises the view and entity of the subject partaking of an object, the subject being the actor and enjoyer, while the object what is seen/tasted/imagined. Then with the changing of the object, for instance finishing a glass of apple juice, the subject loses its reason to exist and experiences some dissatisfaction because of that. All this can go down in a few seconds from seeing the apple juice to having drunk it. And then it happens again and again with the various experiences happening, the previous conditioning the next.

Chan by Investigating Body and Mind

 “You only have to carefully look inside of yourself (反觀) and examine skandhas, āyatanas and dhātus one by one: is there a tiniest thing to be obtained?” 

[The guest] replied: “I have carefully contemplated it, and have not seen anything which can be obtained.”

 The Master said: “Have you destroyed the characteristic of the mind and body?” 

[The guest] answered: “The nature of the mind and body is such that they disappear by themselves, what is there left to destroy?” 

The Master asked: “Is there any thing outside the mind and body?” 

[The guest] answered: “The mind and the body have no outside, how could there be any thing?” 

The Master asked: “Have you destroyed the mundane characteristic?” 

[The guest] answered: “The mundane characteristic is the absence of characteristics, what is left there to destroy?” 

The Master said: “If so, than you have overcome the mistake.”

(source: The Chán Teaching of Nányáng Huìzhōng (-775) in Tangut Translation by Kirill Solonin; also found in Records of the Transmission of the Lamp, vol 7, 28.1; T51n2076p438c26-439a2)

Will All Attain Enlightenment?

In the Saccasaṁyutta there are a series of suttas (SN 56.61-131) on the rarity of the precious human birth, like how few are born as humans (SN 56.61; see also the blind turtle simile: SN 56.47-48), not in a borderland (SN 56.62), and with wisdom (SN 56.63), and among those passing away as humans many are reborn in the lower realms and few in the heavens (SN 56.102-107). On the other hand, attaining insight is supremely difficult (SN 56.45) but without it there is no liberation (SN 56.44). At the same time, speculating about various matters of the world is not beneficial for the path, rather one should get busy with understanding the Dharma (SN 56.41).

The Buddha was asked (AN 10.95): 'when Master Gotama teaches in this way, is the whole world saved, or half, or a third?'
And Ananda explained: 'it’s not the Realized One’s concern whether the whole world is saved by this, or half, or a third. But the Realized One knows that whoever is saved from the world—whether in the past, the future, or the present—all have given up the five hindrances, corruptions of the heart that weaken wisdom. They have firmly established their mind in the four kinds of mindfulness meditation. And they have truly developed the seven awakening factors. That’s how they’re saved from the world, in the past, future, or present.'