2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/163867Ordinary first-order logic has the property that two formulas ϕand ψhave the same meaning in a structure if and only if the formula ``ϕiff ψ'' is true in the structure. We prove that independence-friendly logic does not have this property.18 pages. Submitted to the Journal of Symbolic LogicLogictext