One is often said to be reasoning well when they are reasoning logically. Many attempts to say what logical reasoning is have been proposed, but one commonly proposed system is first-order classical logic. This Element will examine the basics of first-order classical logic and discuss some surrounding philosophical issues. The first half of the Element develops a language for the system, as well as a proof theory and model theory. We provide theorems about the system we developed, such as unique readability and the Lindenbaum lemma. We also discuss the meta-theory for the system, and provide...