Deceiving their own souls
This is properly an instance of the first sort of enthusiasm: it is a kind of madness arising from the imagination that they have that grace which in truth they have not, so that they only deceive their own souls. Madness it may justly be termed, for the reasonings of these poor men are right, were their premises good. But as those are a mere creature of their own imagination, so all that is built on them falls to the ground. The foundation of all their reveries is this: they imagine themselves to have faith in Christ. If they had this, they would be kings and priests to God (Revelation 1:6), possessed of a kingdom which cannot be moved (Hebrews 12:28). But they have it not. Consequently all their following behavior is as wide of truth and soberness as that of the ordinary madman who, fancying himself an earthly king, speaks and acts in that character.
1771 text
14. This is properly an instance of the first sort of Enthusiasm: it is a kind of madness, arising from the imagination, that they have that grace which in truth they have not: so that they only deceive their own souls. Madness it may justly be termed: for the reasonings of these poor men are right, were their premises good: but as those are a mere creature of their own imagination, so all that is built on them falls to the ground. The foundation of all their reveries is this: they imagine themselves to have faith in Christ. If they had this, they would be Kings and Priests to God, possest of a kingdom which cannot be moved. But they have it not. Consequently, all their following behaviour, is as wide of truth and soberness, as that of the ordinary madman, who fancying himself an earthly King, speaks and acts in that character.