 Artemov’s (2008) framework of justification logic shares many surface similarities with Gabbay’s system of labelled deduction. The logic is composed of justification assertions of the form \(x : A\), read as \(x\) is a justification for \(A\). Justifications themselves are evidential bases of varying sorts that will vary depending on the context. They might be mathematical proofs, sets of causes or counterfactuals, or something else that fulfils the justificatory role. What it means for \(x\) to justify \(A\) is not analysed directly in justification logic. Rather, attempts are made to characterise the justification relation \(x : A\) itself, via various operations and their axioms. The application operation, ‘.’ mimics the application operation ‘+’ from labelled deduction, or the fusion ‘\(\otimes\)’ operation from categorial information theory. In justification logic, the symbol ‘+’ is reserved for the representation of joint evidence. Hence ‘\(x + y\)’ is read as ‘the joint evidence of \(x\) and \(y\)’. Application and join are characterised in justification logic by the following axioms respectively: 