In a new book, Sen. John McCain (R-AZ) writes that his battle with brain cancer has given him a sense of liberation to vote and speak his mind.

“This is my last term,” McCain writes in his upcoming book The Restless Wave, which he co-authored with former adviser Mark Salter. An excerpt of the book was posted Monday on Apple News.

“If I hadn’t admitted that to myself before this summer, a stage 4 cancer diagnosis acts as ungentle persuasion,” McCain continues. “I’m freer than colleagues who will face the voters again. I can speak my mind without fearing the consequences much. And I can vote my conscience without worry. I don’t think I’m free to disregard my constituents’ wishes, far from it. I don’t feel excused from keeping pledges I made. Nor do I wish to harm my party’s prospects. But I do feel a pressing responsibility to give Americans my best judgment.”

The book, which comes as McCain remains in Arizona undergoing treatment, includes sharp shots at President Donald Trump, according to the Apple News write up. “He has declined to distinguish the actions of our government from the crimes of despotic ones,” McCain writes. “The appearance of toughness, or a reality show facsimile of toughness, seems to matter more than any of our values.”

Describing the political environment overall, the Arizona Republican writes that he is dismayed by the “scarcity of humility in politics these days.”

“I suspect it’s never been in abundant supply in most human enterprises,” McCain writes according to the excerpt. “And I don’t mean modesty. Any politician worth a damn can fake modesty. Humility is the self-knowledge that you possess as much inherent dignity as anyone else, and not one bit more. Among its other virtues, humility makes for more productive politics.”

In a seeming nod to his physical condition, McCain writes of his desire “to see our politics begin to return to the purposes and practices that distinguish our history from the history of other nations.” Before he “leaves,” he added, “I would like to see us recover our sense that we are more alike than different.”

“We are citizens of a republic made of shared ideals forged in a new world to replace the tribal enmities that tormented the old one,” McCain writes. “Even in times of political turmoil such as these, we share that awesome heritage and the responsibility to embrace it.”