Invalid arguments

All baseballs are round.
The moon is round.
Therefore, the moon is a baseball.

The president lives in the White House.
Barack Obama lives in the White House.
Therefore, Barack Obama is the president.

Arguments like these are not valid. They are called INVALID ARGUMENTS.

It's pretty obvious that the first example is wrong, because we all know that the moon is not a baseball! But this is not why the argument is invalid. It is invalid because the premises don't support the conclusion, not because its conclusion is obviously wrong.

The second argument might seem like a good one because we know the conclusion is true. Barack Obama is president right now. But you should always remember, in a valid argument the conclusion must be PROVEN by the premises.

Does the fact that Barack Obama lives in the White House prove he is president? No. Because Michelle Obama, his wife, also lives in the White House. And his daughters Sasha and Malia also live there. But they are not the president.

Examine the following invalid argument.

A peach is a type of fruit.
Peaches are yellow.
Therefore, all yellow fruits are peaches.

Can you explain why this is an invalid argument?

This may not seem like a big deal. After all, we all know that bananas are also yellow. So, who cares? The problem is when people make invalid and unsound arguments about important things, or when they try to trick you or persuade you about things that are not quite so obvious as baseball moons and yellow watermelons. This sort of persuasion happens every day, especially in things like advertising, retail stores, social issues, religion and politics.