Paradox ~A statement that seems contradictory or absurd but is actually valid or true. At the most basic level, a paradox is a statement that is self contradictory because it often contains two statements that are both true, but in general, cannot both be true at the same time.
“We must sometimes be cruel to be kind…”
“By doing nothing, I have achieved much…”
Antithesis ~The placing of a sentence or one of its parts against another to which it is opposed to form a balanced contrast of ideas.
“Give me liberty or give me death.”
“Listen, young men, to an old man to whom old men were glad to listen when he was young.”
“It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all going direct the other way.” (Dickens)