Adam Sandler movies, HBO's Entourage, and such magazines as Maxim and FHM all trade in and appeal to one character--the modern boy-man. Addicted to video games, comic books, extreme sports, and dressing down, the boy-man would rather devote an afternoon to Grand Theft Auto than plan his next career move. He would rather prolong the hedonistic pleasures of youth than embrace the self-sacrificing demands of adulthood.

When did maturity become the ultimate taboo? Men have gone from idolizing Cary Grant to aping Hugh Grant, shunning marriage and responsibility well into...