 This suggests adopting the following rule for determining the truth-value of complex propositions some of whose constituents are neither true nor false. One considers in turn each of the possible ways in which things may turn out, and works out what truth-value the complex proposition would then have. If it turns out to be true in every case, it is true; if it turns out to be false in every case, it is false; otherwise it is neither true nor false (van Fraassen 1966).