All six quotations decoded, each with the speaker and the year where it matters. Worth reading even for the ones you cracked, since two of them are routinely misquoted.
CiphertextSlhpmfiqf cg khpfn.
PlaintextKnowledge is power.
— Francis Bacon
CiphertextG yfgum, yfzlzitlz G xr.
PlaintextI think, therefore I am.
— Rene Descartes
CiphertextVzev od xtp dfebb dvpy sxa e fet.
PlaintextThat is one small step for a man.
— Neil Armstrong, Apollo 11 (1969)
CiphertextCua mgairjtgax wtna tl gec sevcu wtotgb.
PlaintextThe unexamined life is not worth living.
— Socrates
CiphertextInu abgk inxbd vu nlwu ia quls xe quls xieugq.
PlaintextThe only thing we have to fear is fear itself.
— Franklin D. Roosevelt (1933)
CiphertextJbt kqm xfjm dqya lqykmad ljk hq zqa dqy.
PlaintextAsk not what your country can do for you.
— John F. Kennedy (1961)