Blackwell Reference Online

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The word ‘logic’ in the title of this chapter is ambiguous. In its first meaning, a logic is a collection of closely related artificial languages. There are certain languages called first-order languages , and together they form first-order logic. In the same spirit, there are several closely related languages called modal languages, and together they form modal logic. Likewise second-order logic, deontic logic and so forth. In its second but older meaning, logic is the study of the rules of sound argument. First-order languages can be used as a framework for studying rules of argument; logic done this way is called first-order logic. The contents of many undergraduate logic courses are first-order logic in this second sense. This chapter will be about first-order logic in the first sense: a certain collection of artificial languages. In Hodges (1983) , I gave a description of first-order languages that covers the ground of this chapter in more detail. That other chapter was meant to serve as an introduction to first-order logic, and so I started from arguments in English, gradually introducing the various features of first-order logic. This may be the best way in for beginners, but I doubt if it is the best approach for people seriously interested in the philosophy of first-order logic; by going gradually, one blurs the hard lines and softens the contrasts. So, in this ... log in or subscribe to read full text