Interesting question! I'd say the most fundamental principles are simpler. Avoiding evil, do good, purify the mind. And I'd reduce that to avoiding harming others, to begin with, i.e harmlessness. It seems from evidence in the suttas that the Buddha didn't teach the deep topics such as causality or even the four noble truths until he knew that the listener's mind was ready to receive them.
I think there is an MN sutta that lists 60(?) pairs of attributes that one should develop or abandon, and it starts with harmlessness. "Others will be harmful, we here will be harmless" or something like that. In his talk on that sutta, Bhikkhu Bodhi said that harmlessness is considered to be the fundamental starting point, if I recall correctly.
p.s sorry for the paraphrasing on the sutta, best I can do at the moment. If anyone thinks I've misrepresented the Buddha's teaching, please clarify.
I hope that every time I post it will be accompanied by a wish for the wellbeing of everyone in this sangha and all beings.
(so I don't have to write "metta" every time!)
Kammalakkhano , bhikkhave, bālo, kammalakkhano pandito, apadānasobhanī paññāti
(The fool is characterized by his/her actions/the wise one is characterized by his/her actions/Wisdom shines forth in behaviour.)
(AN 3.2 Lakkhana Sutta)