Practical dealings demand difference-awareness while shared ground enables any joint action.

Evidence

We depend on the observation of their differences if we want to use them and adopt the right attitude toward them. Our practical interest concentrates on what gives us advantages and disadvantages in our dealings with them, not on that in which we coincide. Similarity, rather, provides the indispensable condition for any developing action whatever. — Georg Simmel, The Sociology of Georg Simmel, 1817

Categorization

• XREF: Parallel to the dyad/triad logic: similarity (dyadic union) is the silent precondition, while difference (which needs a third or contrastive observer) propels action.