Enthusiasm
Luther's category (Schwärmerei) for the claim to have the Holy Spirit apart from the external Word and sacraments: direct revelation, inner light, a voice in the heart. He regarded it as the oldest error there is, and insisted God comes to us from outside ourselves, through preaching, water, bread, and wine, precisely so that we are not left to authenticate our own religious experience.
In Doctrine — What Lutherans teach, and where it differs from neighbouring traditions.