 In Bolzano’s view, propositions can be expressed more or less adequately by sentences, and consideration of linguistic structures accordingly informs his treatment of the parts and structures of propositions. Consider a sentence such as ‘Romeo loves Juliet’, for instance. We recognize that we could replace ‘Romeo’ with another proper name such as ‘Othello’ and still have a perfectly grammatical sentence. Moreover, given a set of proper names, we can specify a class of sentences that differ from ‘Romeo loves Juliet’ at most by having a different one of those names at the beginning. We could proceed similarly with ‘loves’ and a suitable set of transitive verbs. Or we could consider the class of sentences obtainable when both sorts of replacements are permitted, and so on. These classes of sentences would correspond to the sentential forms ‘a loves Juliet’, ‘Romeo V Juliet’, and ‘a V Juliet’, respectively.