On the notion of justification

Suppose we are prepared to conceive the meaning of a sentence as a classification criterion which enables us to establish whether something is or is not a justification to believe that sentence. Which properties of the intuitive notion of justification to believe a sentence are essential from this point of view? And how might a theoretical notion of justification for a sentence be defined? In Sections 2-5 some properties are suggested as essential, in particular Intentionality (a justification is always a justification for a sentence), Defeasibility (a justification for a sentence A can cease to be a justification for A as new information is received), and Epistemic transparency (a justification for A is not a justification for A unless it is recognized as such by an idealized knowing subject). In Section 6 the sketch of a definition is proposed, according to which a justification for a sentence A is a cognitive state in which the subject has at his disposal a certain amount of information, and the hypothesis that A is the best explanation of that information. Section 7 shows how the notion defined escapes a crucial objection to defeasible justifications recently stated by P. Casalegno.