In the fields of logic, rhetoric, and philosophy, a sound argument is one that is both correctly formed and contains all true premises.
An argument with a correct form is called valid. However, it is possible to have a valid argument that is not sound.
A valid but not sound argument:
1. I am a doctor.
2. All doctors are smart.
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3. Therefore, I am smart.
The conclusion follows from the statements, and if statement 1 and 2 were true, then this argument would be sound. However (at least) statement 1 is false. Therefore, this argument is unsound. It should be noted this argument is both valid and the conclusion is true. However, no matter how obvious 3 may be, I have not yet proven it through means of logical argument.