attributing a fundamental epistemic function to the sign, claiming that “all instruction is either about things or about signs; but things are learnt by means of signs” (Omnis doctrina vel rerum est vel signorum, sed res per signa discuntur) (Augustine De doctr. chr. I 1, 1963, 9). The borderline between things and signs and thus the sign itself is defined functionally rather than ontologically: signs are things employed to signify something