The Three Dharma Seals are basic to all Buddhism. They are one of the reasons that Buddhism is sometimes called a philosophy rather than a religion. Faith is not required to understand the Three Dharma Seals. We can prove them to ourselves through thought and observation.
The Three Dharma Seals are impermanence, lack of self-nature, and nirvana. The Three Dharma Seals are ultimate truths. They are called “Dharma Seals” because all things are “stamped” with them; there is nothing that does not possess these three ultimate characteristics. Another reason that Buddhist call these three truths “Dharma Seals” is they are similar to official seals that prove documents are real and not forged. If any so-called “truth” contradicts the Three Dharma Seals, then it cannot be an authentic teaching of Shakyamuni Buddha. Any “truth” that is not stamped with all three of the Three Dharma Seals cannot be true. Even if the Buddha himself were heard to say a “truth” that contradicts the Three Dharma Seals, that “truth” could not be true. In this same vein, any truth that is stamped with all three of the Three Dharma Seals must be true, whether a Buddha said it or not. The Three Dharma Seals are so fundamental to Buddhism that it can further be said that any truth that is stamped with the Three Dharma Seals is a Buddhist truth; it is good Buddhism and can be taken to be part of the Dharma.
The Truth of Impermanence
The First Dharma says that all phenomena are impermanent. This means that all phenomena change. Nothing stays the same. All phenomena are constantly interacting with each other, constantly influencing each other, and constantly causing each other to change. The First Dharma Seal also says that each and every phenomenon is changing from one moment to the next.
The Truth of No Self-Nature
Not only are all things impermanent, but they are also all devoid of a self-nature. Having no self-nature means that all things depend on other things for their existence. Not one of them is independent and able to exist without other things. The meaning of the word “things” in these statements is all phenomena, both formed and formless, all events, all mental acts, all laws, and anything else you can think of.
To say that nothing has a self-nature is to say that nothing has any attribute that endures over long periods of time. There is no “nature” that always stays the same in anything anywhere. If the “nature” of a thing cannot possibly stay the same, then how can it really be a nature? Eventually everything changes and therefore nothing can be said to have a “nature,” much less a self-nature.
The Truth of Nirvana
As finger points to the moon, so the Third Noble Truth points to Nirvana. The Third Noble Truth is not itself nirvana, but it does tell us something about nirvana. Nirvana means the “cessation of suffering.”
Since suffering is caused by delusion, nirvana also means the cessation of delusion. Since suffering is caused by belief in duality, nirvana also means cessation of duality, or the belief in duality. Nirvana means cessation of belief in a separate self, cessation of the birth and death of the “self,” and cessation of belief in a permanent absolute anything anywhere. Nirvana is normally described only by what it is not because nirvana is not a deluded state.