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Conditional Logic 101

Many statements on the LSAT are conditional statements, so it's important to learn to identify conditional statements and even more important to know what to do with conditional statements when they do pop up! Today's post is all about the basics of conditional logic and how to diagram conditional statements.


Let's consider the following statement: If Jane goes to the movies, she wears a purple dress.


The "if" part of the conditional statement is known as the sufficient condition, while the "then" part of the conditional statement is known as the necessary condition. If the sufficient condition is met, the necessary condition must also occur.


Now on to diagramming!


The point of diagramming a conditional statement is to understand the relationship between the terms. Traditionally, we use an arrow to represent the idea of conditionality, placing the sufficient condition to the left of the arrow and the necessary condition to the right of the arrow. When it comes to diagramming conditional statements for the LSAT, don't waste time writing out every word of the statement! Remember, the LSAT tests both accuracy and speed. Instead, you want to devise a simple shorthand that you can understand. I typically use the first letter of key terms or phrases in the statement to make my diagrams. In this case, I picked out "movies"(represented by M) and "purple dress" (represented by PD) as the key components of the conditional statement. Thus, my diagram looks as follows:


Don't worry if this short hand seems odd to you at first. Like all things on the LSAT, practice makes progress! But before you sit down to do some practice, let's look at a few trickier forms of conditional statements and the corresponding diagrams.


Consider the following statement: Natalie will go to the party if John goes to the party.


This example emphasizes the point that conditional statements are about the relationship between ideas. Notice that this statement does not follow the traditional "if... then" format from our previous example. Instead, the statement is worded such that the necessary condition is followed by the sufficient condition. Despite this, the diagram still places the sufficient condition to the left of the arrow and the necessary condition to the right of the arrow:

Let's look at another one: All of the boys in Mrs. Greyson's class are 9 years old.


In this example, there is no "if" to tip you off that this statement is conditional. However, there is an "all," which is another example of a conditional indicator word that you should have memorized by test day. ”All” introduces the sufficient condition, meaning that “The boys in Mrs. Greyson’s class” is our sufficient condition, and “9 years old” is the necessary condition. So our diagram looks as follows:




There are certainly more complex sentence structures and indicator words that are trickier to diagram, such as “unless,” but this post is meant to be an introduction to conditional logic and diagramming. Tips on how to diagram other sentences, especially ones with the word “unless” will be in a new post soon! Until then, take some time to practice the conditionals in the worksheet that I have provided. With enough practice, diagramming conditionals will become second-nature to you!


Happy LSAT studying! XO Payten

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