Write two arguments in English, one in the form of modus ponens and one in the form of modus tollens. Then, write the arguments in symbols using sentence letters and truth-functional connectives. (If your computer does not have all the symbols needed, use some other symbol you do have access to and explain what its meaning is.)What advantages does being able to symbolize our arguments provide? Are there disadvantages to using this technique to make the structure of our arguments more explicit and clear?
The Logic of Sentences
We begin by seeing how to apply symbols—sentence letters—to sentences, first using basic sentences and then using sentences constructed out of these basic sentences.
Assertoric Sentences and Sentence Letters
Earlier we looked at various strings of words: some were questions, some were commands, and some were assertions. Here are some examples of the kinds of sentences we examined earlier, as well some new, compound sentences, which assert more than one claim: