Dual avoidance

In dual avoidance, a Black defense seems to allow several White replies, often several mating moves. A full reading of the position shows that only one reply is legal or effective. Every other candidate fails because of a particular consequence of that defense.

A candidate may be excluded because the defense guards a square, closes a line, immobilizes a unit that cannot move without exposing its king, opens an escape square for the king, or permits another answer to the supposed mate. A different reply may work in another variation. The theme depends on making the apparent alternatives visible and separating them precisely.

If two replies genuinely work in the same variation, the result is a dual, not avoidance. Dual avoidance is therefore a deliberate display of uniqueness. In cyclic forms, three or more mates exchange roles: a mate that is real in one variation appears as an excluded possibility in another, and the pattern closes into a cycle.