  The distinctive features of quantum mechanics, which set it apart from other
physical theories, challenge our notions of realism. Recovering realism from
purely philosophical grounds, a quantitative and operational criterion was
proposed in the past, but solely for the context of quantum mechanics. We use a
framework of generalized probabilistic theories to expand the notion of realism
for a theory-independent context, providing a criterion uniquely based on the
probabilities assigned to measurement outcomes. More so, using robustness and
the Kullback-Leibler divergence, we propose quantifiers for the realism of
arbitrary physical properties given a particular state of a generic physical
theory. These theory-independent quantifiers are then employed in quantum
mechanics and we investigate their relation with another well-established
irrealism measure.
