Fig 4. Composition and causal relations.

Relations between distinctions specify joint causes and/or effects. The two distinctions d(a) and d(aB) each specify their own cause and effect. In this example, their cause and effect purviews overlap over the unit b and are congruent, which means that they all specify b to be in state “-1.” The relation r({a, aB}) thus binds the two distinctions together over the same unit. Relation faces are indicated by the blue lines and surfaces between the distinctions’ causes and/or effects (different shades are used to individuate the faces). Because all four purviews overlap over the same unit, all nine possible faces exist. Note that the fact that the two distinctions overlap irreducibly can only be captured by a relation and not by a high-order distinction.