The essay analyzes the central methodological issues of Amartya Sen's Capability Approach and identifies the distinction between basic and non-basic value judgments as the interpretative key for understanding the intertwining of facts and values that characterizes the notions of functioning and capability. By highlighting the importance of the factual presumptions underlying value judgments, Sen elucidates the non-basic nature of the principles of collective choice. According to Sen, a widely use of non-basic value judgments and principles allows: the possibility of a rational discussion on value judgments; the broadening of informational basis for weighted and shared choices about functionings and capabilities in different life contexts; the obtaining of rules – at the analytical as well as practical levels – that satisfy reasonable requirements in consonance with the methodological indications of Aristotle's practical philosophy. Non-basic value judgments instantiate Sen’s advocacy of incompleteness as an essential feature of evaluative exercise.
