Abstract

There is a specific class of propositions frequently used but almost unknown from the point of view of formal logic. Suppose that A, B, C are names. The propositions “A is B qua C” and “A qua C is B” are called qua-propositions. Roberto Poli introduced the term “qua-theory” in order to separate the special part of logic as well as philosophy focused on qua-propositions – their logical properties and meaning. But as long as some kinds of qua-propositions are not distinguished, the subject of qua-theory cannot be established properly and clearly. In my article I want to examine the proposals of Roberto Poli and Allan Bäck and in effect to propose different classifications of qua-propositions. Also the epistemological context will be important. Different kinds of qua-propositions enable us to distinguish different kinds of epistemological views very generally called “aspectualism”