Justification logic and the epistemic contribution of deduction

TL;DR

This paper develops a justification logic framework to explain how deduction contributes to knowledge, emphasizing the importance of justification for each step in the derivation rather than mere logical consequence.

Contribution

It introduces a novel justification logic system that captures the epistemic contribution of deduction by focusing on the justification of each step in the reasoning process.

Findings

A new justification logic system for deduction

Clarification of how deduction adds epistemic value

Addressing the problem of knowledge gain through deduction

Abstract

Accounting for the epistemic contribution of deduction has been a pervasive problem for logicians interested in deduction, such as, among others, Jakko Hintikka. The problem arises because the conclusion validly deduced from a set of premises is said to be "contained" in that set; because of this containment relation, the conclusion would be known from the moment the premises are known. Assuming this, it is problematic to explain how we can gain knowledge by deducing a logical consequence implied in a set of known premises. To address this problem, we offer an alternative account of the epistemic contribution of deduction as the process required to deduce a conclusion or a theorem, understanding such process not only in terms of the number of steps in the derivation but, more importantly, the reason for or justification for every step. That is, we do not know a proposition unless we have a justification or proof to hold that proposition. With this goal in mind, we develop a justification logic system which exhibits the epistemic contribution of a deductive derivation as the resulting justified formula.