'Spiritual Enlightenment' can be defined as gaining the perfect knowledge about the four noble truths or about life.
As Buddhism teaches, no one can't give this perfect knowledge with words or even with telepathy. Individuals have to gradually self-realize it. Only some approximate assumptions can teach according to the teacher's teaching power. Those assumptions can be;
All worldly things are Impermanent, suffering and non-self.
Cycle of death-rebirth is suffering, Suffering is due to cravings, Cravings can be overcome, Path to overcome the cravings is the Threefold Training (or Noble Eightfold Path).
Practice moral virtue (Five precepts, Eight precepts etc.), Get higher level of mind concentration (Samatha Meditation), Get higher wisdom to analyze these assumptions (Vipassana meditation). These three steps can’t be separated such as complete one and then complete other. These three steps have to develop cyclically again and again till the enlightenment.
Self-view of the Citta sequence existed for a very long time, without any beginning in the cycle of rebirth. So, it is difficult to remove this self-view. Buddhism defines a living being in different ways to give a better realization. We previously defined a living being as combinations of non-materiel and material things exist as generations without any permanent part. (There is a non-ending huge sequence of Citta connected with a living being. When sensation this Chitta stream shifts to different places to process the sensation. When a being is living, a huge amount of sensation processes arises.)
According to Buddhism there are six sense bases. Those are eye, ear, nose, tongue, body, and mind. In this definition, we think a living being as a stream of ever changing five types of collections connected within six sense bases. Those collections are; Material form or corporeality(sense triggers), feelings(pleasure, displeasure or neutrality), perception(recognition with mental labels), mental formations(mental factors that are required to do an action) and consciousness(knowings or mind). This collection is called ‘Five Aggregates’. Buddhism defines a living being as a huge collection of five aggregates without any soul.
[ Each of aggregate has collations from past, percent and future. We have to consider these five aggregates in time and place wise five bundles (Khandha Sutta , Maha-punnama Sutta). ]
1. Material form or corporeality (Rupa)
Here we consider all of the substantial entities of matter collectively. All of these things aren’t permanent and always change from one state to another. When we think past, percent and future with the place of arising there is a bundle of material phenomena related to a living being. This bundle is the first aggregate.
2. Feelings (Vedanā)
The sensory experience of an object is either pleasant, unpleasant or neutral. When we think past, percent and future with the place of arising there is a bundle of feelings. This bundle is called the feeling aggregate.
3.Perception (Saññā)
A mental label that recognizes an object is called Saññā. Saññā helps to recognize an object. There are millions of types of Saññā. E.g; the shape of a tree, houses, sounds, colours,..etc. Education will acquire more and more Saññā. Then he may become more egotistical. When we think past, percent and future with the place of arising there is a bundle of Saññā. This bundle is called the perception aggregate.
4. Mental formations (Saṃskāra)
A motive or intention with which an action is doing called Cetanā. All actions (E.g; speech, eat, read) start with a Cetanā. But support from mind and other mental factors are required to do an action (here Karmas may generate). Mind and other mental factors with the leading Cetanā related to an action is called Saṃskāra.
When we think past, percent and future with the place of arising there is a bundle of Saṃskāra. This bundle is called the Mental formations aggregate.
5.Consciousness (Viññāna)
For a normal being, there are six internal-external pairs of sense bases(doors) as follows;
eye and visible objects
ear and sound
nose and odor
tongue and taste
body and touch
mind and mental objects(such as past memories)
One of six kinds of trigger came from one of six external sense bases (Ayatana). Then it causes a sense trigger in one of internal sense bases. Then one sensation process starts. Chitta stream will shift and process the sensation with many thought processes (Chitta-viti). To see an image, many thought processes are arised. (When we are sleeping, such as when there is no trigger from the eye, ear, nose, tongue, body or mind, the Chitta stream only contains Bhavanga-Chitta. Bhavanga-Chitta always exists from the conception when there is no thought process. Bhavanga-Chitta doesn’t allow the Chitta stream to stop.)
When a trigger arises in a sense door, sensation will happen with many thought processes. For an example; when an object appears in front of the eyes, a series of consciousness arises, which recognizes the object. This series of consciousness is called "eye-consciousness". Ordinary people call this as “vision” rather than a series of consciousness.
Mind is similar to sequence of consciousness or Viññāna. Here we consider all of knowings(or recognitions) as the consciousness aggregate.
When we think past, percent and future with the place of arising there is a bundle of consciousness. This bundle is called the consciousness aggregate.
“These material forms are not me. There is no part within material forms which can be treated as me.”
“These feelings are not me. There is no part within feelings which can be treated as me.”
“These perceptions are not me. There is no part within perceptions which can be treated as me.”
“These mental formations are not me. There is no part within mental formations which can be treated as me.”
“These consciousnesses are not me. There is no part within consciousness which can be treated as me.”
“All of these five aggregates are not me. Those are just results of some causes. These five aggregates are impermanent, suffering and non-self.”
“There is nothing to take as me. All things are just results of some causes. All things are Impermanent, Suffering and Non-self.”
Two causes of past lives
1) Ignorance
2) Karmic Formations
Five percent results since past causes
3) Rebirth-consciousness (first mind of a new birth)
4) First materiel embryo base unit and mind base five aggregates,
5) Arising sense spheres; eye, ear, nose, tongue and skin
6) Sense spheres triggers or contacts
7) Feelings
Three cause of current life
8) Craving
9) Grasping
10) Good or Bad Karmas case to a birth
Two future results since cause of current life
11) Birth
12) Ageing & Death
If we could perfectly remove “1) Ignorance” with getting perfect knowledge about life, then there will not be any greed or anger in the sequence of consciousness. Then there are no “2) Karmic Formations”. Then there will not be “3) Rebirth-consciousness”. Then there will not “4) First materiel embryo atom”. … Finally there will not be “12) Ageing & Death” or any kind of suffering. We have to repeatedly think ‘Dependent Arising’ top to bottom and bottom to top.
Enlightenment is the final result of the gradual process of all Threefold Trainings (Noble Eightfold Path). For example; Clean defilement, Gain mind concentration, Gain knowledge, Increase awareness and realize the reality in some amount. Again, Clean more defilement, Gain more mind concentration, Gain more knowledge, Increase the awareness and have a better realization about the reality, …..
There are Seven Factors of Enlightenment:
Mindfulness (Sati)
Investigation of Dhammas/Reality/”Four Noble Truths” (Dhamma-vicaya)
Energy to continue (Viriya)
Joy or rapture (Pīti)
Relaxation or tranquility of both mind and body (Passaddhi)
Mind Concentration gained with meditation (Samādhi)
Equanimity maintain all of these factors(Upekkha)
To experience the final Magga-citta, it is important to develop all of these factors in a balanced way. Reading this answer will develop your 2nd factor 'Investigation of Dhammas'. But this doesn’t develop other factors in a balanced way. So most likely, you will not experience a Magga-citta. But, if you have developed other factors before in this life or in a previous life, there is a possibility of experiencing a Magga-citta with balancing all factors. (After doing meditation, you can calmly try reading this answer again. But for someone, it may need many years of practice to reach a Magga-citta.) Lord Buddha teaches us the best way to develop these factors is “Four Mindfulness Meditation” or Satara-Satipatthana Meditation. (Please study Satipatthana-Sutta. Also there is a free 10-day course from www.dhamma.org with worldwide locations.)
This kind of assumption knowledge (also called 'Parathogoshaka-Prathya'), can only be given by a rightly self-awakened Lord Buddha or by his disciple. This answer has enough assumption knowledge for an extremely intelligent person to reach Enlightenment without doing hard practices in the 'Threefold Training'.
During the cycle of rebirth almost all time, a being can't hear these Dharma(assumptions) since Lord Buddhas are very rare. No one can self-realize these assumptions since the all ignoble beings (almost all of us) always live with different kinds of defilements (such as; greed, hatred, or delusion) even without knowing. You may think I don’t have a lot of defilements such as greed. But lots of them exist in a tiny manner without knowing. I personally think, if Lord Buddha could not come to the word, currently our world may be like a terrorist area. If so, we can't hear words like Four Noble Truths and Enlightenment. I think also words like Donations will be rare.
The time we can hear these assumption words (Buddha's Dispensation) are like an instant when compared to the cycle of rebirth. For a very intelligent person, these assumptions are like divine nectar since these words can remove all infinite amounts of sufferings he has to face in the cycle of rebirth.
When a person reaches Enlightenment, he will become free from all kinds of sufferings permanently after his current life. He will be permanently happy. So, enlightenment can be defined as gaining eternal happiness. Also when attaining Enlightenment all of his cravings will vanish. So, enlightenment can also be defined as removing all kinds of cravings.
There are five stages of enlightenment. First four stages (Stream-enterer, Once-returner, Non-returner, Arahant) are called ‘Sopadisesa-Nirvana’. Last and final stage is the passing away from the last body and called ‘Anupadisesa-Nirvana’.
