How to answer "must be true" questions on the LSAT

The LSAT is a challenging exam, and one of the most challenging questions on it asks “must be true.” These types of questions are difficult when you don’t know how to answer them. When answering these questions, there are three things that you should keep in mind: 1) the first sentence must be an accurate statement about how to solve this type of question, 2) some statements may not be true but if they’re not necessary for solving the problem then it doesn’t matter how untrue they are, 3) some statements might seem like false opposites or contraries which would make them impossible to affirm as true.

These are a type of Logical Reasoning questions that use soft and undefined informal logic – including unstated assumptions and observations. Formal Logic is what a computer would do: hard, logic-following rules. Formal logic is prevalent in the legal world.

The first sentence of how to solve must be true questions is that you need to know how the question prompt will tell you how many answers are being asked. The second statement might not be totally accurate, but it’s important for understanding how to answer these types of questions. Sometimes they’ll have more than one correct answer so focus on what makes the most sense.

Here’s an example on a must be true question on an LSAT:

“If all dogs are mammals, then no reptiles are dogs. No snakes or lizards are dogs. Therefore some animals that aren’t dogs must be reptiles.”

This is how to answer this type of question: one way to do it would be to list out the elements of the statement like so: if (A)

then (B) and not C, therefore D. A is “All dogs are mammals”; B says that no reptiles are a dog; C states that there must be some reptile out there since all non-dogs have been eliminated as being a mammal or a dog which leaves us with the conclusion of D: “therefore some animals that aren’t dogs must be reptiles.

In conclusion, when trying to answer “must be true” questions on the LSAT,  you should always list out the elements of how it is structured and how to properly break down each element.