Strong vs. Valid.

With given premises, in any way, is the conclusion false?

If you answer “yes” to the question above, you get invalid arguments that can be strong (or weak). If you answer “no,” you get a valid argument.

Valid argument: No possible way for the premises to be true and the conclusion false (at the same time); in other words, if the premises are true then conclusion should also be true.

Exampleà This school only allows students to wear khaki pants and a black shirt as a uniform. Therefore, all the students going to this school wear khaki pants and a black shirt.

*If the premises of the school only allowing students to wear wear khaki pants and a black shirt as a uniform is true, then the conclusion of all the students going to the school wear the khaki pants and a black shirt should also be true.

Strong argument: A possible way for the premises to be true and the conclusion false (at the same time), though these possibilities are very unlikely; the premises are true, but the conclusion can and may also be false.

ExampleàAll the students my friend and I have seen at this school wear khaki pants and a black shirt. Therefore, all the students going to this school wear khaki pants and a black shirt.

*It is possible the my friend and I have seen all the students at the school wear khaki pants and a black shirt, but the conclusion of all the students going to the school wear khaki pants and a black shirt can and may be false.

Strong arguments (with true premises) can sometimes be better than valid ones that both end with the same conclusion.

Also, when deciding if an argument is strong or valid, it does not depend on:

1. if the premises are true,

2. if we know the premises are true, and

3. if the person making the arguments believes the argument is valid or strong.