Principium Cognoscendi Internum
The human mind, before the internal testimony of the Spirit, could not receive the Word. Something, indeed, has been changed within the soul that now makes it receptive to the gospel. The full development of this discussion belongs, of course, to soteriology, but the identification of the subjective ground of reception does belong to the principial and preliminary sections of theological system.
Richard A. Muller, Post-Reformation Reformed Dogmatics: The Rise and Development of Reformed Orthodoxy; Volume 1: Prolegomena to Theology, 2nd ed. (Grand Rapids, MI: Baker Academic, 2003), 442–443.