Week 5 Session: Opposites and Neighbors — Relationships Among the Trigrams

How do the eight trigrams relate to each other, independent of how they are arranged?

22 March 2027

The question#

Before asking how the eight trigrams are laid out, what relationships hold between them regardless of layout?

What this builds on#

Week 4 gave you all eight trigrams as objects. This week looks at the structure between those objects, which any later arrangement (Xiantian in week 6, Houtian in week 7) has to be consistent with, not invent.

One relationship, four pairs#

With only two line values, there is exactly one way to take a trigram’s “opposite”: flip every line. Applied to the eight trigrams from week 4, this produces four pairs, each trigram paired with the one that shares none of its lines: Qian ☰ (all yang) with Kun ☷ (all yin); Zhen ☳ with Xun ☴; Kan ☵ with Li ☲; Gen ☶ with Dui ☱. This is the trigram set’s one clean relationship that doesn’t depend on arrangement — it follows from the line values alone, the same construction rule from weeks 3–4, not from anything added on top.

It is worth being precise about what this relationship is not. Some accounts of the Bagua describe trigrams as standing in “complementary opposition” without specifying whether that means this same line-inverse relation under another name, or something about where trigrams sit relative to each other once arranged in space. This course uses one term — line-inverse — for the one relationship that is genuinely independent of arrangement, and holds off on any second, spatial notion of “opposite” until an arrangement actually exists to be opposite within. Week 6 is where that spatial question becomes answerable: watch, when the Xiantian arrangement is introduced, whether these same four inverse pairs end up placed opposite each other on the circle, or not.

What you should be able to do after this week#

Identify a trigram’s line-inverse and name the four inverse pairs among the eight trigrams. Keeping this relationship separate from arrangement matters: it is a property of the trigrams themselves, true before either of the two arrangements the course studies next is imposed on them.