  Counterfactual definiteness (CFD) means that if some property is measured in
some context, then the outcome of the measurement would have been the same had
this property been measured in a different context. A context includes all
other measurements made together with the one in question, and the
spatiotemporal relations among them. The proviso for CFD is non-disturbance:
any physical influence of the contexts on the property being measured is
excluded by the laws of nature, so that no one measuring this property has a
way of ascertaining its context. It is usually claimed that in quantum
mechanics CFD does not hold, because if one assigns the same value to a
property in all contexts it is measured in, one runs into a logical
contradiction, or at least contravenes quantum theory and experimental
evidence. We show that this claim is not substantiated if one takes into
account that only one of the possible contexts can be a factual context, all
other contexts being counterfactual. With this in mind, any system of random
variables can be viewed as satisfying CFD. The concept of CFD is closely
related to but distinct from that of noncontextuality, and it is the latter
property that may or may not hold for a system, in particular being contravened
by some quantum systems
