Found among my notes while clearing off my desk:
The following propositions seem to be essential to the nature of protestantism:
Scripture is transparent (perspicuous) and self-authenticating.
The real church is invisible.
The central axiom of faith is forensic justification.
Sacraments are signs, but cannot either be changed ontologically, or ontologically change the believer who receives them.
None of the above statements are true. For example,
An invisible church is a disembodied church; a disembodied church is a disincarnate church; and a disincarnate church is a docetic church. Such a church cannot be a trustworthy bearer of the gospel of the incarnate God.