 In the following we will see several proposed models for the structure of belief. Most of these proposals take the objects of belief to be either  propositions, or  sentences in a formalized language. This section reviews the basic notions required to work with propositions and sentences in a formal language. If the reader feels overwhelmed with the technicalities in this section, they should feel free to postpone them, and refer back to it on-the-fly. Readers who are accustomed to working with these objects may freely skip this section.