Bar mitzvah is simply the age when a person is held responsible for his actions and minimally qualified to marry. If you compare this to secular law, you will find that it is not so very far from our modern notions of a child's maturity. In Anglo-American common law, a child of the age of 14 is old enough to assume many of the responsibilities of an adult, including minimal criminal liability. Under United States law, 14 is the minimum age of employment for most occupations (though working hours are limited so as not to interfere with school). In many states, a fourteen year old can marry with parental consent. Children of any age are permitted to testify in court, and children over the age of 14 are permitted to have significant input into custody decisions in cases of divorce.