What makes an argument valid or invalid? Why is validity important in Logical Reasoning? This LSAT learning resource will teach you how to differentiate a valid argument from an invaluable argument on logical reasoning questions. By the end, you'll be able to confidently analyze arguments and make informed judgments.
A valid argument provides all the information needed to prove its conclusion. In a valid argument, if the premises are true, the conclusion must be true as well.
Some valid arguments are more intuitively valid than others. Here’s a valid argument that you probably have no problem accepting:
1. Ralph is a dog.
2. No dogs are allowed on the roller-coaster.
3. Therefore, Ralph is not allowed on the roller-coaster.
The following argument, though counterfactual, is also 100% valid:
1. Every dog is a reptile.
2. Every reptile is cold-blooded.
3. Therefore, every dog is cold-blooded.
Each of the arguments above is valid because the truth of its premises guarantees the truth of its conclusion.
Of course, in the second example above, the premises are false. But that doesn’t mean it’s an invalid argument. On the LSAT, your job isn’t to argue with the premises. Your job is to accept the premises and to object when those premises don’t prove the conclusion. Read more about attacking the argument here.
