When I first enrolled in Taekwondo back in 2001 when I arrived in San Angelo, I took classes from an instructor who may have been skilled in Taekwondo. However, as many people no doubt have picked up over the years, skill at an activity does not equate to the ability to teach said activity (see, e.g. Thomas, Isaiah).
When I started up with Taekwondo again back in 2012, it came as some surprise to me that the was more to the art than just learning patterns and how to defend one's self. I learned that there were principles, a dogma, to Taekwondo - which are referred to as the "tenets" of Taekwondo.
Perhaps these tenets are not universal to all schools or forms of Taekwondo, but I've since come to find the same tenets referenced by other schools, both in ITF and WTF styles.
The Tenets of Taekwondo, as our school teaches them, are as follows (please forgive any misspellings on the hangul, it's been over a decade since I used it with any semblance of regularity):
Ye Ui (예의) = Courtesy
Yom Chi (렴치) = Integrity
In Nae (인내) = Perseverance
Guk Gi (극기) = Self-Control
Baekjul Boolkool (백절 불 굴) = Indomitable Spirit
While our school expounds on these tenets, I will not repost what the school wrote, however, in the event there are questions as to what is meant by any particular tenet, I will be willing to share my personal take on any one or more.