The LSAT is many things—stressful, annoying, repetitive, fun(?), to name a few—but at its core, it’s a very learnable exam. Once you master key concepts and strategies, your goal score will [almost] be within reach. 

One of those key concepts is logical force, which is really just a fancy term for the strength of a statement. If you can understand and apply logical force, your score might just increase a good five points on your next practice exam. 

So let’s get into it!

What is Logical Force?

Logical force measures how strong a statement is. We classify that strength as weak, moderate, or strong, and we look at two dimensions of a statement: how broad it is and how certain it is. Let’s use some examples.

How certain are you of the weather tomorrow?

• It might rain tomorrow. (weak, >0% chance)
• It will probably be chilly tomorrow. (moderate, >50% chance)
• The sun will definitely rise tomorrow. (strong, 100% chance)

How many of your cousins are fun?

• Some of them have good taste in music. (weak, >0)
• Most of them are sports fans. (moderate, >50% of them)
• None of them are jerks. (strong, 100% of them)

Using Logical Force on the LSAT

But why is logical force so important on the LSAT? Well, it’s all about the structure and validity of arguments, i.e. the key elements that make or break your case in and out of the courtroom. 

Validity is the golden ticket here. It’s when the conclusion is guaranteed if the premises (support/evidence) are true. But guess what? If the conclusion tries to flex stronger logical force than its premises, the argument is automatically invalid! Period.  

Now, let’s apply this wisdom to the LSAT, specifically in the Logical Reasoning section. Armed with your knowledge of logical force, you’ll easily spot those shaky arguments where the conclusion is reaching too far without proper support.

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Let’s dive into some specific question types to show why logical force is going to be your new LSAT bestie.

Inference questions? Yeah, they’re no match for you now! Remember, your conclusions can’t be stronger than the premises, and inference questions ask you to draw a valid conclusion based on the premises they’ve given you. You can immediately eliminate answer choices stronger than the text.

Assumption questions are all about finding the perfect match. Necessary assumptions need an answer choice that is not stronger than the conclusion. (Think of it this way, you don’t NEED $25 support to afford a $10 conclusion. It helps, but it’s not necessary.) But sufficient assumptions can bring even more logical force than the conclusion itself! Sufficient means enough, so a strong assumption will be enough to prove a moderate conclusion, as long as it’s relevant.

You can also use logical force to break down Strengthen and Weaken questions. The stronger your evidence, the better job it does of helping strengthen your argument. Same thing with weaken questions. What’s going to do more to convince you your friend’s lying when they say their new rescue cat is friendly, hearing that it occasionally hisses at strangers or that it always attacks new faces?

It also pays off in the Reading Comprehension section for inference questions and “What we can conclude from the passage” questions. Remember, we can’t conclude anything with stronger logical force than our support, which in this case is the passage. 

For agreement questions, whether it be something the author would agree with or another viewpoint holder would agree with, it’s still easier to agree with a weak statement than a stronger statement so you can also use your elimination on really strong logical force answer choices, and go for a weaker statement related to what that viewpoint holder was arguing in the passage.

So if you’re trying to score some quick wins and easy points, watch this video for more help with logical force, and then channel your inner detective and get better at spotting the logical force of premises and conclusions. 

If you want to try it on some real LSAT questions, create a free Blueprint LSAT account to access a free practice exam with a full performance breakdown so you know exactly what your strengths and weaknesses are.