Man has been called a rational being, but rationality is a matter of choice - and
    the alternative his nature offers him is: rational being or suicidal animal. Man
    has to be man - by choice; he has to hold his life as a value - by choice; he has to
    learn to sustain it - by choice; he has to discover the values it requires and
    practice his virtues - by choice.

    -- Ayn Rand, "Galt's Speech," Atlas Shrugged