Simo Knuuttila 
Modalities in Medieval Philosophy [PDF ebook] 

Originally published in 1993, Modalities in Medieval Philosophy looks at the idea of modality as multiplicity of reference with respect to alternative domains. The book examines how this emerged in early medieval discussions and addresses how it was originally influenced by the theological conception of God acting by choice. After a discussion of ancient modal paradigms, the author traces the interplay of old and new modal views in medieval logic and semantics, philosophy and theology. A detailed account is given of late medieval discussions of the new modal logic, epistemic logic, and the logic norms. These theories show striking similarities to some basic tenets of contemporary approaches to modal matters. This work will be of considerable interest to historians of philosophy and ideas and philosophers of logic and metaphysics.