The article aims to show that the term, "incommensurability", used by Kuhn provides, together with the concept of "comparability", conditions for an objective choice between theories. It defends that Kuhn's philosophy is not a relativist. I discuss the notions of incommensurability in the broad sense and of local incommensurability. I make use of an event in the history of astronomy connected with Copernicanism to illustrate that the empirical adequacy allows comparison between locally incommensurable theories.
Kuhn; Incommensurability; Comparability; Dynamic of theories; Objectivity; Copernicanism