This is the first post in a series that focuses on the LSAT. Each post in this series contains an excerpt from our new Guide to Formal Logic on the LSAT; this focuses on if/then statements in conditional logic. If you would like to download the full guide, please use the form at the bottom of this post.
By far, the most commonly tested type of formal logic on the LSAT is the conditional statement. It is found in abundance in both Logic Games – particularly in grouping games – and in Logical Reasoning. Conditional statements can essentially be boiled down to “if/then” statements, or what must follow from a given condition. We use the following structure when we diagram such statements:
if –> then
If you live in Brooklyn, then you live in New York City.
If you live in Brooklyn –> then you live in New York City
When actually diagramming these for the test, we’re going to remove the words “if” and “then.” Instead, we’ll remember that the left of the arrow means if, and the right of the arrow means then, yielding:
Live in Brooklyn –> Live in New York City
Diagram the following examples:
- If you don’t include the broth, the meal will be incomplete.
- The dinner will start at 8 if Daniel is on time.
- ~Broth –> Incomplete. ~Incomplete –> Broth
- Daniel’s on time –> Start at 8. ~Start at 8 —> ~Daniel’s not on time.