Many people often wonder how to tell the difference between a paradox and an oxymoron. There's no quick and easy rule, like with alligators and crocodiles, but with a few examples I think I can show that anyone can tell the two apart.
Oxymorons are phrases that, though used often, contradict themselves.
The best rule of thumb is to look at the first word and then the second and see if they mean two completely different things. Paradoxes are much, much different, in that they often require many words, even a whole paragraph to explain them. Paradoxes are much more dangerous than oxymorons. Many movies have been made about paradoxes destroying the universe but none about oxymorons hurting even one person even a little. The best source for information about paradoxes is Star Trek .