Absolute trust that pardon is already obtained is not the essential formal act of justifying faith
Weak true faith can temporarily lack absolute assurance of already-obtained pardon.
Therefore that assurance is not faith’s essential formal act.
Latin
XXI. Porro cum fides vera, licet infirma, saltem ad tempus consistere possit absque fiducia certa & absoluta de obtenta a Deo remissione peccatorum, & nostra per Christi gratiam reconciliatione, inde patet fiduciam istam non esse essentialem & formalem actum fidei salvificae atque justificantis. Nec enim fides justificans unquam consistere potest sine actu suo proprio & formali.