**An argument is valid =df If all the premises are true, then the conclusion must be true**. 2. An argument is valid =df It is impossible for all the premises to be true but the conclusion false.

## What is an example of an invalid argument?

An argument is said to be an invalid argument if its conclusion can be false when its hypothesis is true. An example of an invalid argument is the following: “**If it is raining, then the streets are wet.** **The streets are wet.**

## How can you decide if an argument is valid or invalid?

Judge the reasoning and not the content (true or false statements). Think hypothetically. Ask, “IF the premises are true, are we locked into the conclusion?” If yes, then the argument is valid. If no, then the argument is invalid.

## Can an invalid argument form be valid?

An invalid argument form is one that does have substitution instances with true premises and a false conclusion. The conclusion is false in lines 2 and 4. In each of these lines, there is also a false premise. **Since there is no substitution instance with true premises and a false conclusion, the argument form is valid**.