Lecture Notes by Christopher Lay

Los Angeles Pierce College

Department of History, Philosophy, and Sociology

Mathew Van Cleave's 2016 Introduction to Logic and Critical Thinking

https://open.umn.edu/opentextbooks/BookDetail.aspx?bookId=457

Excerpts from Chapter 2 "Formal Methods of Evaluating Arguments," § 7 "Conditionals" 

According to my New Oxford American Dictionary, a condition is "a state of affairs that must exist or be brought about before something else is possible or permitted."

"A sufficient condition is a condition that suffices for some other condition to obtain."

"A necessary condition is a condition that must be in present in order for some other condition to obtain." 

"To say that x is a necessary condition for y is to say that if x were not present, y would not be present either." 

[Incidentally, "[t]he consequent of a conditional statement always lays down a necessary condition."]