ABSTRACT
In this chapter we develop a technique for testing the validity of a limited class of arguments. To characterize the class in question we need to consider one way in which indicative sentences of English can be formed. There are words or sequences of words which themselves do not constitute sentences but which can be used to construct sentences if put together in the appropriate way with a sentence or sentences. For instance, the word ‘and’ can be used to generate a sentence by putting sentences before and after it as in ‘Icabod is a student and Icabod is rich’. Similarly the phrase ‘Icabod believes that’ which is not a sentence can be used to generate a sentence if we put a sentence after it as in ‘Icabod believes that students are exploited’. We will call such expressions sentence-forming operators because they operate on sentences to give more complex sentences. A sentence-forming operator is a word or sequence of words which is not a sentence but which when appropriately concatenated with an indicative sentence or sentences gives an indicative sentence of English. Other examples of sentence-forming operators are: It is not the case that, or, if … then …, it is possible that, Icabod hopes that, because.
