1002 Lecture : philosophy note
Document Summary
The syntax for the language sl contains two kinds of rules. There are formation rules, which tell us how to string the vocabulary elements together to create those well-formed expressions that we call sentences. There are also rules of a different sort: the sentential derivation or sd rules. The two sets of rules are made for entirely different purposes and may not be mixed with one another. Whereas the formation rules tell us how to build sentences out of vocabulary elements, the derivation rules state conditions under which we can derive sentences from other sentences or, in some cases, from nothing at all. The study of derivations brings us to the heart of what logic is traditionally considered to be: the study of reasoning. We will eventually use the derivation system, sd, to symbolize how we draw conclusions when we reason in english. There are two parts to the study of reasoning.