One of the three characteristics of existence is anattā i.e., non-self. It means that all formations (saṅkhāras) in this world are impermanent (anicca), subject to suffering (dukkha) and without a self (anattā). It means that they do not have any permanent self.
Let us first understand what is ‘self’ and what does it do to us? Changes inside us take place so rapidly that we are not able to see them. Since we can't grasp a change which is taking place continuously at a tremendous speed, we just grasp the continuity and we think we are permanent just as a rapidly rotating torch gives the impression of being a ring of fire. In the same manner, we consider we are permanent but this is an illusion. Reality is completely different from it. When we do understand that there is no permanent self in us then we will understand that there is no ‘I’. If there is no ‘I’ then isn’t it foolish on our part to say ‘This is mine’, ‘this is me’ and ‘this is my self’ as shown in the Majjhima Nikāya (1.189).
The Buddha has explained what anattā is in the Anattalakkhaṇa Sutta of Saṃyutta Nikāya (2.61). There he explained why there is no self (anattā). He takes each of the five aggregates which constitute our being and shows that none of them can claim to be attā.
“Bhikkhus, form is non-self. For if, bhikkhus, form were self, it would not lead to affliction, and it would be possible to have it of form: ‘Let my form be thus; let my form not be thus.’ But because form is non-self, form leads to affliction, and it is not possible to have it of form: ‘Let my form be thus, let my form not be thus.’”
In the same way he shows that neither feeling nor perception, nor volitional formations nor consciousness is self. Had they been so, it would have been possible for one to command them to behave the way one liked. But this is not possible. One’s body is afflicted even though one wants it not to be so. Pleasant sensations do change to unpleasant ones even though one does not want them to change. So is the case with perception, volitional formations and consciousness. As far as consciousness is concerned, it changes more quickly than body (rūpa). One does not have any authority on any of the aggregates, even less so on consciousness. Therefore, how can one claim them to be one’s self. They do not behave the way one likes them to behave. They always elude him. When rūpa (form) arises, even if one wants it to stay it does not, nor does it not-become old even if he wants it to not become old, nor is it not-destroyed even if he does not want its destruction. It is never tired of arising and passing away. The same thing happens with the rest of the aggregates. They are not under one’s control. Therefore, they are not one’s self.
In the three verses beginning with ‘sabbe saṅkhārā aniccāti’, ‘sabbe saṅkhārā dukkhāti’ and ‘sabbe dhammā anattāti’, the Buddha says that all saṅkhārās and conditioned dhammās are impermanent and cause suffering and they do not have any permanent self. Even unconditioned dhammā is without a self. That is why he uses the word dhammā in the third verse. All dhammās, conditioned and unconditioned, are without any self. When one sees this with wisdom, one is disgusted with suffering and develops virāga (non-attachment). This is the path of purification. This is the path to eliminate all defilements that are at the root of suffering.
Contemplation of anicca leads one not to believe in the first cause because there is nothing permanent; contemplation of dukkha makes one realistic, makes one know its cause, know also that if cause is eliminated suffering will end and also know the path leading to the cessation of suffering. It also makes one detached. When there is no attachment, no clinging, there is no agitation. When there is absence of agitation, one experiences peace. And contemplation of anattā makes one unattached and unselfish.
But contemplation does not mean intellectual understanding. One may understand intellectually that all conditioned things are impermanent. But that does not help much. One has to understand it at the experiential level. While practicing vipassana one can see clearly how sensations arise and pass away, how impermanent they are, how even pleasant sensations arise and pass away giving place to unpleasant ones. One sees dukkha clearly. Unpleasant sensations obviously cause dukkha but pleasant sensations too cause dukkha when they change to unpleasant ones. When one realizes anicca he understands that there is no-self. There is anattā only. This realization has tremendous impact on him. The scales from his eyes fall. He becomes disillusioned and comes out of the shell of ignorance, which is the root cause of our suffering. He develops non-attachment and becomes free from all cravings. The cycle of birth and death stops forever as it is completely annihilated.
A vipassanā meditator can easily experience anicca and dukkha. He can also experience anattā by trying to steady his pleasant sensations but when he tries to do so, they elude him. It then dawns upon him that there is nothing in one’s being on which he has any control. All aggregates that make up one’s body are without any attā (self). Thus, practice of vipassanā enables him to realize the three characteristics of all phenomena.
What are the other advantages of contemplating tilakkhaṇa? The Buddha describes its advantages effusively in so many passages of the Tipiṭaka. In the Anicca Sutta of Saṃyutta Nikāya (Khandha vagga 2.21), he says, “Seeing thus, bhikkhus, the instructed noble disciple experiences revulsion towards form, revulsion towards feeling, revulsion towards perception, revulsion towards volitional formations and revulsion towards consciousness. Having experienced revulsion, he becomes dispassionate. Through dispassion, his mind is liberated. When it is liberated, there comes the knowledge ‘It’s liberated.’ He understands: ‘Destroyed is birth, the holy life has been lived, what had to be done has been done, there is no more for this state of being.’”
In the same Nikāya of Dutiya Anicca Sutta, he describes other advantages in detail. “When one sees this thus as it really is with correct wisdom, one holds no more views concerning the past, one holds no more views concerning the future. When one holds no more views concerning the future, one has no more obstinate grasping. When one has no more obstinate grasping, the mind becomes dispassionate towards form, feeling, perception, volitional formations and consciousness, and is liberated from the taints by non-clinging. By being liberated, it is steady; by being steady, it is content; by being content, one is not agitated. Being unagitated, one personally attains Nibbāna. One understands: ‘Destroyed is birth, the holy life has been lived, what had to be done has been done, there is no more for this state of being.’” (Bhikkhu Bodhi, The Connected Discourse of the Buddha, p. 885)
The Buddha had developed revulsion for all phenomena by realizing with the help of bhāvanāmayā paññā their three characteristics at the experiential level and became liberated. Realization of these three characteristics can enable one to end one’s own suffering.