I present two logical systems to show the “analogy of proportionality” common to several interpretations: modality (necessity and possibility), quantification, truth-functional relations, moral attitudes (deontic logic), states of knowledge (epistemic logic), and states of belief (doxastic logic). To display the two underlying analogical relations, I call upon the originally Scholastic convention, recently put to use again, of using squares, hexagons, and octagons “of opposition”. A combined epistemic–deontic logic happens to be found in the traditional “probabilist” theory of the “good conscience”, and I shall then briefly explain how this is so.
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