Over time, lexical items are recycled and take on different or additional meanings from the ones they originally had. Somewhat surprisingly, items may take on converse meanings. This is the case with the prepositions besides and beyond, which may signal either inclusion or exclusion, depending on the context. An etymological examination shows that over time, both words have undergone semantic extension from their original spatial meanings. Syntactically, the primary functions of the two are as prepositions and adverbs. Quantitative results show that while nowadays beyond functions primarily as a preposition, besides functions equally often as an adverb and a preposition. The converse meanings of besides and beyond are shown here to depend on whether the context is assertive or non-assertive. Both words form part of a large group of prepositions of inclusion and exclusion which share both semantic and syntactic features. Syntactically, what is remarkable about all of them is their ability to occur not only with nominal complements but also with that-clauses, bare infinitives, and adjective phrases. One of the issues discussed in this article is what is the best syntactic analysis of these structures.