  Existence of physical reality in the classical world is a well-established
fact from day-to-day observations. However within quantum theory, it is not
straightforward to reach such a conclusion. A framework to analyse how
observations can be described using some physical states of reality in a theory
independent way was recently developed, known as ontological framework.
Different principles when imposed on the ontological level give rise to
different observations in physical experiments. Using the ontological
framework, we formulate a novel notion of classicality termed "universal
classicality" which is based upon the physical principles that in classical
theories pure states are physical states of reality and every projective
measurement just observes the state of the system. We construct a communication
task in which the success probability is bounded from above for ontological
models satisfying the notion of universal classicality. Contrary to previous
notions of classicality which either required systems of dimension strictly
greater than two or atleast three preparations, a violation of "universal
classicality" can be observed using just a pair of qubits and a pair of
incompatible measurements. We further show that violations of previously known
notions of classicality such as preparation non-contexuality and Bell's local
causality is a violation of universal classicality.
