An Easy Guide to Principle/Application Questions

Last week, we went over principles in LSAT logical reasoning. Today, let’s talk about questions that give you a principle and an application right there in the stimulus. It looks something like this:

Principle: Anyone who has been drinking to excess should drink several glasses of water before going to sleep.

Application: Mick has been at his friend’s birthday party all night. Therefore, Mick should drink plenty of water before he falls asleep.

This format scares a lot of LSAT students because they think that there’s something different or special about questions presented this way. There isn’t. The principle and application, together, comprise an argument. The principle is a premise. The application has a conclusion and often has additional premises. Put them together and you can treat the resulting argument like you’d treat any argument on the LSAT.

The Principle-Application format, therefore, isn’t its own question type. Rather, it can show up across a number of question types. Most common are Strengthen (“The application of the principle would be most justified if which of the following were true?”), Sufficient Assumption (“Which of the following, if true, would justify the application of the principle?”) and Flaw (“The application of the principle is vulnerable to criticism because”).

While these questions don’t require any special approach, there are some patterns that might make them easier. Principles are often conditional statements, and these arguments often have one of the two following flaws:


This is the flaw in the example above. The principle talks about drinking to excess. The application only tells us that Mick was at a party. The assumption is that if Mick goes to his friend’s birthday, he’ll drink to excess. If it’s a Strengthen or Sufficient Assumption, expect the answer to make that link. If it’s a Flaw question, the answer will point out that gap.

Sufficiency and Necessity

This flaw shows up in Flaw questions but not so much in Strengthen and Sufficient assumption questions. It goes something like this:

Principle: A college student should retake a class only if he or she is confident in getting a higher grade.

Application: Jane got an A- in sociology, but she’s confident that she could get an A or maybe an A+ if she took the class over. Therefore, she should retake the class.

The problem with this argument isn’t Jane’s absurdly high standard for herself, it’s that the principle identifies necessary conditions, not sufficient ones, to retake a class. It would diagram as:

                Retake → confident in higher grade

Therefore, it doesn’t matter how confident you are of a higher grade. That’s never going to be enough to say you should retake. The argument’s flaw is that it treats a necessary condition, confidence in getting a higher grade, as if it were sufficient. You don’t see this kind of argument in Strengthen and Sufficient Assumption questions because there’s really no way to fix it. The principle just goes the wrong way.

But keep in mind that if there’s conditional logic in the stimulus, they’ll usually describe a conditional fallacy in the answers whether there is one or not. Make sure the argument really did mix up a conditional statement before you accuse it. The real flaw might be something else.

All in all, when you seen a principle and application, don’t freeze or change anything up. Just identify the question type and then treat the stimulus as you’d treat any other argument on the LSAT.

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