 Owing to the plurality of the objects of a single judgment, it follows that what we call a “proposition” (in which it is to be distinguished from the phrase expressing it) is not a single entity at all. That is to say, the phrase which expresses a proposition is what we call an “incomplete” symbol; it does not have meaning in itself, but requires some supplementation in order to acquire a complete meaning. (Whitehead and Russell 1910–13, 43–44)