What are Holden's foundational values?

Holden believes in kindness, authenticity, and protecting the innocent.
For example, as he is leaving Pencey, he is kind to his history professor, Mr. Spencer, when he asks Holden if he read the history textbook:

"Well, I sort of glanced through it a couple of times," I told him. I didn't want to hurt his feelings. He was mad [in love with] about history.

Another example of his kindness is his concern over the nuns he meets while eating a huge breakfast at a New York diner. They are eating a small breakfast, and Holden worries they may be hungry. He likes them for their sincerity and ends up giving them a generous donation for the convent. He also helps two rough, lower class boys who are cutting school find the "mummies" at the Metropolitan Museum of Art, even though they end up running off.
Holden despises people who are "phony." An example would be his roommate Ward Stradlater, the "secret slob," who is willing to lie and cheat to get ahead. Holden gets upset when he finds out that Stradlater, the "sexy bastard," is taking his friend Jane Gallagher out on a date. Holden fears Stradlater will use his phoniness to take advantage of her.
Holden also hates phony language. For instance, when Mr. Spencer calls Holden's parents "grand," Holden thinks:

Grand. There's a word I really hate. It's a phony. I could puke every time I hear it.

Holden is driven by a desire to protect the innocent, especially children. This comes from his brother's death and his sense of his helplessness in preventing it. He dreams of being the catcher in the rye, the person who saves children before they can innocently run off the edge of a cliff. He is very protective towards anyone who he senses is vulnerable, young or old, and especially wants to protect his sister Phoebe.
There is a saying that states "no good deed goes unpunished." Holden is always, in small ways, doing kind deeds or saying kind words to the people around him, most of whom don't notice and treat him less kindly than he deserves.

Some of the values that Holden cherishes throughout the novel include honesty, authenticity, and humility. Holden views most adults as phonies and cannot stand superficial people. His adolescent mindset affects his ability to compromise and fully understand the social aspects of the adult world. The only person Holden is truly close with is Phoebe, and he appreciates her genuine, compassionate nature. Similar to most children, Phoebe is brutally honest, and Holden can trust her.
He views the majority of adults as being manipulative and selfish, which affects his willingness to enter adulthood. Holden also believes that his brother is a talented writer but disagrees with his decision to move to Hollywood because he feels like D.B. sold out. Holden views the entertainment industry with contempt and does not respect his brother's decision to enter a superficial society. Holden also values humility and believes the majority of people with confidence are arrogant. He disagrees with America's views regarding success and feels like the world of adults is simply a rat race. Overall, Holden builds his foundation on honesty, humility, and authenticity. It is important to remember that while Holden respects and cherishes these character traits, he is a hypocrite and does not necessarily live up to these values.