The Core Principles are a list of characteristics that all Lumon Industries employees and followers of Kier Eagan are expected to demonstrate. These principles are intended to unite and inspire those who adhere to them, and to lead them to become better people and more industrious workers.

There are nine Core Principles. They are:

1. Vision
2. Verve
3. Wit
4. Cheer
5. Humility
6. Benevolence
7. Nimbleness
8. Probity
9. Wiles

The Core Principles are comparable to the Seven Virtues of Catholic theology. There is one virtue which directly overlaps with the Core Principles, humility.

The Core Principles feature prominently in documents intended for severed employees. These include the Compliance Handbook and The Macrodata Refiner’s Orientation Booklet. The principles are designed to intertwine and overlap, as they should all be considered together instead of separately. There is an emphasis on good social skills, because employees are considered not just a team, but a community or family.

In Half Loop, Irving mentions that a fun fact about him is he knows all nine Core Principles. When Milchick asks him which is his favorite, Irving responds, “All nine. But today, I think I’d say, “cheer”.”

In In Perpetuity, the Eagan Bingo cards Dylan distributes have a square for the Core Principles being mentioned in the Perpetuity Wing.

The Core Principles are also intended for followers of Kier Eagan. Harmony Cobel in particular demonstrates repeatedly how an exemplary follower should use the principles to structure and guide their life. In The You You Are, Cobel calls on the principle of wiles before attending Peter Kilmer's funeral in order to retrieve his severance chip. In Hide and Seek, she mentions that Mark's valiance in trying to take Ms. Casey's place in the Break Room is “not a core principle, but sweet.”

There are also several examples of the principles being shown in Cobel's home. Again in Hide and Seek, we see a framed needlepoint above Cobel's bed that lists them. Her Shrine to Kier also repeatedly features all nine principles, as seen in her handmade posters and collected Kier memorabilia.

Cobel was presumably indoctrinated in the Core Principles during her time at the Myrtle Eagan School for Girls.