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Laws / rules / logic / Wessel: Law = tautology, with operators
I 50 Rules: statements about formulas (formulas themselves do not appear as formulas, but as quotations) = equivalences. "Equivalence" is not an operator.
Law / Wessel: always logical form of implication - (x) (P (x) > Q (x) - although not all true implications are laws - when a law has the form of an implication it cannot be a statement of the form Q (a) where a is an individual constant.
Logik Berlin 1999