  We propose a definition of determinism for a physical system that includes,
besides the measured system, the measurement device and the surrounding
environment. This enlarged system is assumed to follow a predefined trajectory
starting from some (unknown) initial conditions that play the role of hidden
variables for the experiment. These assumptions, which are different from
realism, allow us to derive some Leggett-Garg inequalities, which are violated
by Quantum Mechanics in the particular case of consecutive measurements on
individual photon polarizations.
