Mandatory diagnostics

A common observation plateau therefore does not force equality of arbitrary responses produced by different switch histories. For example, changing $g$ by a small bump in a compact causal-past region, while keeping both switches equal to one near a later observation, changes ${\partial }_t(g\psi )$ in (eq:sourced). A nonzero resulting response can be detected by a later test. Causal-past agreement, not only agreement near the observation, is sufficient for equality; this distinction is also retained in VII-A-ST VIIAST.