Here are some key elements that support the Tuck's claim:
* The Family's Appearance: The Tucks don't age. Winnie observes their unchanging appearance over multiple encounters. They appear as if they've been frozen in time.
* The Spring's Properties: The Tucks' immortality is tied to the magical spring water. Winnie witnesses firsthand its effects on the woodchuck and feels its effects on herself.
* The Tuck Family's History: The Tucks have been living for centuries, which supports their claims of immortality. They have a rich history, including the story of Mae's death and resurrection.
* The Tuck Family's Knowledge: They have a vast knowledge of the world and its history, which suggests they have lived long enough to accumulate it.
* The Tuck Family's Behavior: Their actions and choices reflect their understanding of their unique situation, like their resistance to sharing the spring's secret and their attempts to protect Winnie.
* The Mysterious Circumstances: The novel mentions the Tucks' past, suggesting they have been involved in strange events that tie into their immortality.
* The "Tuck's" World: The world around the Tuck family is described as unchanging, suggesting that they have lived through the passage of time without actually aging.
Ultimately, the novel asks the reader to suspend their disbelief and accept the possibility of the Tucks' immortality based on the details presented, rather than providing nine specific events as hard evidence.