«وشرطه: اللزوم الذهني»
Its condition is mental necessitation.
Luzūm dhihnī (اللزوم الذهني) requires a mental link by which understanding the stipulated meaning makes the additional implication intelligible. The point is not merely an observed coincidence between two things.
Not every implication is apprehended equally quickly. Some are obvious on reflection and others require thought; degrees of clarity are possible. The technical relationship still differs from a chance memory triggered by an expression.