  In the paper, the question whether truth values can be assigned to the
propositions before their verification is discussed. To answer this question, a
notion of a propositionally noncontextual theory is introduced that in order to
explain the verification outcomes provides a map linking each element of a
complete lattice identified with a proposition to a truth value. The paper
demonstrates that no model obeying such a theory and at the same time the
principle of bivalence can be consistent with the occurrence of a non-vanishing
"two-path" quantum interference term and the quantum collapse postulate.
