 For Bolzano every proposition is either true or false, and this forever — or better: timelessly. If we get under certain circumstances the impression that one and the same proposition can sometimes be true and sometimes be false, this is merely due to the fact that we do not talk about a proposition but about an ambiguous linguistic chain of words that expresses two or even more propositions, some of which can be true and others false (WL II, 7). If it is the proposition itself, however, of which we get the impression that it can be true as well as false, this is due to the fact that we take a part of it to be variable (WL II, 77); in this case again we do not consider a single proposition, but a whole set of propositions, i.e., a propositional form. In the expression ‘It is snowing’, e.g., time and place are not determined, and it therefore does not express a proposition, but rather a propositional form, indicated by ‘It is snowing at time \(t\) at place \(l\)’. In order to express a proposition, the variables have to be bound or replaced by constants; Bolzano usually replaces them — for convenience — by indexicals, e.g., ‘It is snowing today and here’ (WL I, 113). Even if Bolzano makes extensive usage of indexicals in the expression of ideas and propositions, there is no place for indexicals within his World 3: There are neither indexical ideas nor indexical propositions; what sometimes seems to be an indexical idea or proposition is in fact merely an indexical expression of an idea or proposition. (See, however, an opposite view defended in Textor 1996.)