These concepts are all interrelated, but if you're looking to join this centuries-old conversation, I'd suggest you start with these 7 key ideas: God, cosmos, nature (human), truth, goodness, beauty, and time. If there were a tree of ideas, these 7 would be main branches.
Related concepts flow from these 7:
God: Authority, Responsibility, Right
Cosmos: Order, Chaos, Cause
Human Nature: Mind, Emotions, Desire
Truth: Knowledge, Definition, Paradox
Goodness: Virtue, Vice, Hierarchy
Beauty: Quality, Fitness, Creativity
Time: Progress, Change, Telos
This isn’t a complete list. Think of it as a prompt to help you build your own. Pay attention to what you (and others) say when angry, excited, or indignant. When people are passionate about something, one of these concepts is always in play, often hiding under the surface.
Mortimer Adler spent 10 years building his list of 102 ideas. His team logged 400,000 hours cataloguing and indexing these concepts. The end result was the Syntopicon. 102 ideas traced across 71 authors, 431 books, and 2,500 years.
The keystone concepts are truth, goodness, and beauty.