This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...of a government: to make social existence possible to men, by protecting the benefits and combating the evils which men can cause to one another.
read full book
The proper functions of a governme
nt fall into three broad categories, all of them involving the issues of physical force and the protection of men’s rights: the police, to protect men from criminals — the armed services, to
protect men from foreign invaders — the law courts, to settle disputes among men according to objective laws.
These three categories involve many corollary and derivative issues...