Every authentic teaching of the Buddha must bear three Dharma Seals: impermanence, non-self, and nirvana.
The first Dharma Seal is impermanence. Nothing remains the same for two consecutive moments. Heraclites said we can never bathe twice in the same river. Confucius, while looking at a stream, said, "It is always flowing, day and night." The Buddha implored us not just to talk about impermanence, but to use it as an instrument to help us penetrate deeply into reality and obtain liberating insight. We may be tempted to say that because things are impermanent, there is suffering. But the Buddha encouraged us to look again. Without impermanence, life is not possible. How can we transform our suffering if things are not impermanent? How can our daughter grow up into a beautiful young lady? How can the situation in the world improve? We need impermanence for social justice and for hope.
If you suffer, it is not because things are impermanent. It is because you believe things are permanent. When a flower dies, you don't suffer much, because you understand that flowers are impermanent. But you cannot accept the impermanence of your beloved one, and you suffer deeply when she passes away.
If you look deeply into impermanence, you will do your best to make her happy right now. Aware of impermanence, you become positive, loving and wise. Impermanence is good news. Without impermanence, nothing would be possible. With impermanence, every door is open for change. Instead of complaining, we should say, "Long live impermanence!" Impermanence is an instrument for our liberation.
The second Dharma Seal is non-self. If you believe in a permanent self, a self that exists forever, a separate, independent self, your belief cannot be described as Buddhist. Impermanence is from the point of view of space. When we look more and more deeply at the notions of self, person, living being and life span, we discover that there are no boundaries between self and non-self, person and non-person, living being and non-living being, life span and non-life span. When we take a step on the green earth, we are aware that we are made of air, sunshine, minerals and water, that we are a child of earth and sky, linked to all other beings, both animate and inanimate. This is the practice of non-self. The Buddha invites us to dwell in mindfulness in the concentrations (samadhi) of interbeing, non-self and impermanence.
The third Dharma Seal is nirvana, which means "extinction," the extinction of afflictions and notions. Human beings' three basic afflictions are craving, hatred and ignorance. Ignorance (avidya), the inability to understand reality, is the most fundamental of these. Because we are ignorant, we crave for things that destroy us, and we get angry at many things. We try to grasp the world of our projections, and we suffer.
Nirvana, the extinction of all afflictions, represent the birth of freedom. The extinction of one thing always brings about the birth of something else. When darkness is extinguished, light comes forth. When suffering is removed, peace and happiness are always there. Many scholars say that nirvana is annihilation, the extinction of everything, and that Buddhists aspire to non-being. They have been bitten by the snake of nirvana.
In many sutras, the Buddha says that although ascetics and brahmans describe his teaching as annihilation and non-being, that is not correct. The Buddha offers us nirvana to rescue us from attachment to the notions of impermanence and non-self. If we get caught by nirvana, how will we ever escape?
Notions and concepts can be useful if we learn how to use them skillfully, without getting caught by them. Zen master Lin Chi said, "If you see the Buddha on your way, kill him." He means if you have an idea of the Buddha that prevents you from having a direct experience of the Buddha, you are caught by that object of your perception, and the only way for you to free yourself and experience the Buddha is to kill your notion of the Buddha. This is the secret of the practice. If you hold onto an idea or a notion, you lose the chance. Learning to transcend your mental constructions of reality is an art. Teachers have to help their students learn how not to accumulate notions. If you are laden with notions, you will never be emancipated. Learning to look deeply to see into the tue nature of things, having direct contract with reality and not just describing reality in terms of notions and concepts, is the practice.
Thich Nhat Hanh