At the beginning of human history, man lost some of the basic animal instincts in which an animal's behavior is embedded and by which it is secured. Such security, like paradise, is closed to man forever; man has to make choices. In addition to this, however, man has suffered another loss in his more recent development inasmuch as the traditions which buttressed his behavior are now rapidly diminishing. No instinct tells him what he has to do, and no tradition tells him what he ought to do; sometimes he does not even know what he wishes to do. Instead, he either wishes to do what other people do (conformism) or he does what other people tell him to do (totalitarianism).
Viktor E. Frankl, Man's Search for Meaning
existentialism