Formal logic including conditional or IF-Then statements appear in 3 out of 4 LSAT test sections. Both Logical Reasoning Sections and the Analytical Reasoning Section will use formal logic. This often includes conditional statements such as “IF Bob is selected THEN Suzie is also selected” or “Suzie is selected IF Bob is selected”
How does this statement differ from “Suzie is selected IF, AND ONLY IF Bob is selected”.
IF AND ONLY IF, is a biconditional statement, meaning that either both statements are true or both are false. So it is essentially and “IF” statement that works both ways.
So our statement “Suzie is selected IF, AND ONLY IF, Bob is selected” means that Suzie and Bob are either both selected or both not selected. There are a variety of standard logical symbols used to represent this relationship including:
“↔”, “⇔” and “≡”, and “iff”
For the purpose of diagramming your LSAT Logic Games we recommend the following:
Note that IF AND ONLY IF is different than simply ONLY IF.
Only If simply creates the reverse statement as if you used “IF”
So the statement “IF Mary is selected then Will is also selected” is the same as “Mary is selected ONLY IF Will is also selected” or “ONLY IF Will is select, is Mary selected”
All of which can be respresented as:
IF M –> W
Greg Smith
Greg took the LSAT in 2002 receiving a high score that got him into the law school of his choice. This led him to teach LSAT classes while attending law school at the University of British Columbia and continued teaching while practicing law with top international law firms Borden Ladner Gervais LLP and later Blake Cassels & Graydon LLP, in the area of Securities and Capital Markets. Read more
