If out of two questions one presupposes the other in such a way that without answering the first one cannot answer the second then the presupposed one has to be treated first. As Russell says the question "What do we mean by truth and falsehood?" is presupposed by others which ask for true judgments, beliefs or opinions:"There is however a preliminary question which is rather less difficult, and that is: What do we mean by truth and falsehood?… we are not asking how we can know whether a belief is true or false: we are asking what is meant by the question whether a belief is true or false."¹