  The Aharonov-Bergmann-Lebowitz rule assigns probabilities to quantum
measurement results at time t on the condition that the system is prepared in a
given way at t_1 < t and found in a given state at t_2 > t. The question
whether the rule can also be applied counterfactually to the case where no
measurement is performed at the intermediate time t has recently been the
subject of controversy. I argue that the counterfactual meaning may be
understood in terms of the true value of an observable at t. Such a value
cannot be empirically determined for, by stipulation, the measurement that
would yield it is not performed. Nevertheless, it may or may not be
well-defined depending on one's proposed interpretation of quantum mechanics.
Various examples are discussed illustrating what can be asserted at the
intermediate time without running into contradictions.
