La costruzione logica del diritto. Proposizioni normative e logica dei sistemi normativi.

A central problem of deontic logic is to reconstruct a notion of normative system (understood as a set of norms, together with their logical consequences) assuming the non-cognitvistic thesis according to which norms are neither true nor false. This work aims to solve this fundamental problem, starting from the key distinction between the concept of norm and the concept of normative proposition (i.e. the meaning of a statement about the existence/validity of a norm within a given normative system). Once I have analyzed (and “de-constructed”) the concept of normative proposition, I’ll examine some of the main proposals to solve this problem put forward within the scope of philosophical logic and analytical jurisprudence. In the first place, I’ll examine the “standard” approach to deontic logic, based on possible-world semantics. I’ll argue that the main flaw of this approach consist in the fact that, within the “standard deontic logic”, norms are deemed to be truth-apt entities – and this collides with the core thesis of non-cognitivism in ethics. Then, I’ll take into account a second attempt to explain the logical relation between the elements of a normative system, based on the so-called Proof-Theoretical semantic theory (developed, first of all, by Prawitz and Dummett); the basic idea of this theory is that the meaning of logical operators (such as deontic modalities) is fixed by the schematic rules for introducing them into a deduction’s premises and conclusions. Lastly, I’ll try to construct a logic for normative systems by adopting the set-theoretical approach developed within the expressive conception of norms (put forward by Alchourrón and Bulygin), and distinguishing between ‘norms’ (understood as results of speech-acts) and ‘normative statements’ (sentences expressing normative propositions). In this alternative reconstruction I’ll discern between two main normative speech-acts (irreducible to one another): command and permission. I will assume, then, that logical relations do not occur between norms but only between the norm-contents which are, depending on the cases, commanded or permitted by a norm-authority. To explain this logical relations between norm-contents I’ll make use of the notions of satisfiability (of norms) and of ‘rational norm-giver’.