The story
In the familiar biography, the prince's father tried to shield him from every sight of suffering, fearing a prophecy that his son would renounce the world. But on outings from the palace, the prince saw an old man, a sick man and a dead body, and learned that no one escapes these. Then he saw a calm wandering renunciant, and understood that there was another way to live.
Where the story comes from
The early discourses do not tell this story about Gotama. The Mahāpadāna Sutta tells it about Vipassī, a Buddha of the distant past, and presents it as a pattern that every Buddha's life follows. Later biographies, such as the Buddhacarita and the Pāli Nidānakathā, gave the same story to Gotama himself.
The early texts do contain something close to it. In a discourse in the Aṅguttara Nikāya, the Buddha recalls his sheltered youth, with a separate palace for each season, and describes how reflecting on old age, sickness and death drained away the pride he had felt in being young, healthy and alive.
Why it lasts
Whatever its origin, the story captures a question every person faces sooner or later: if ageing, sickness and death are certain, how should we live? That question is the starting point of the Buddha's teaching.
Why it matters
They represent the beginning of his spiritual search.
History and tradition
What historians can say
The four sights are a traditional narrative, not an event historians can confirm. They are best read as a teaching story built from themes the Buddha himself taught.
What Buddhist tradition remembers
Buddhist tradition holds that the gods themselves took the form of the old man, the sick man, the corpse and the renunciant, so that the future Buddha would see them.