Shakyamuni preached the Four Noble Truths in his first sermon after attaining Buddhahood.
The Four Noble Truths consist of the following:
Truth of Suffering
Truth of Cause
Truth of Extinction
Truth of the Path
The first of the Four Noble Truths is the Truth of Suffering. This means that all things in this world are comprised of suffering for those who do not listen to the Buddha’s teachings. Human life is filled with spiritual, physical, economic and other forms of suffering. To acknowledge the real condition of suffering and see it through, without avoiding it or meeting it only halfway, this is the Truth of Suffering.
The Truth of Cause means that we must reflect on what causes have produced these human sufferings, and we must investigate them and understand them clearly. The investigation of the cause of suffering is shown clearly in the doctrines of the Reality of All Existence and of the Law of the Twelve Causes explained in chapter 7 of the Lotus Sutra, “The parable of the Magic City.”
The Truth of Extinction is the state of absolute quietude wherein all the sufferings in human life are extinguished. It is the state in which we cut off spiritual, physical, economic, and all other forms of suffering, and realize in this world the Land of the Eternally Tranquil Light (referred to in the Sutra of Meditation on the Bodhisattva Universal Virtue as the land of the Buddha Vairocana). This is a state attained only by awakening to the three great truths that Shakyamuni has taught us: “All things are Impermanent”, “Nothing has an Ego”, and “Nirvana is Quiescence.” These three great truths are also called the “Three Seals of the Dharma”. They are so important that they are be the three fundamental principles of Buddhism.
The Law of the Four Noble Truths teaches us to face the reality of human suffering (the Truth of Suffering), to grasp its real cause (the Truth of Cause), to practice daily the Bodhisattva-way (the Truth of the Path) and thereby to extinguish various sufferings (the Truth of Extinction). The diagram of the Four Noble Truths illustrates this progress.