One is a Buddhist if he or she accepts the following four truths:
All compounded things are impermanent.
All emotions are pain.
All things have no inherent existence.
Nirvana is beyond concepts.
These four statements, spoken by the Buddha himself, are known as “the four seals.” Traditionally, seal means something like a hallmark that confirms authenticity. For the sake of simplicity and flow we will refer to these statements as both seals and “truths,” not to be confused with Buddhism’s four noble truths, which pertain solely to aspects of suffering. Even though the four seals are believed to encompass all of Buddhism, people don’t seem to want to hear about them. Without further explanation they serve only to dampen spirits and fail to inspire further interest in many cases. The topic of conversation changes and that’s the end of it.
The message of the four seals is meant to be understood literally, not metaphorically or mystically—and meant to be taken seriously. But the seals are not edicts or commandments. With a little contemplation one sees that there is nothing moralistic or ritualistic about them. There is no mention of good or bad behavior. They are secular truths based on wisdom, and wisdom is the primary concern of a Buddhist. Morals and ethics are secondary. A few puffs of a cigarette and a little fooling around don’t prevent someone from becoming a Buddhist. That is not to say that we have license to be wicked or immoral.
Source: What Makes You a Buddhist? — Dzongsar Khyentse Rinpoche – Lion’s Roar
