What does it mean for us to be a nation of laws and not of men? This mainstay of our republic takes into account that each one of us, whether beggar or scion, or president of a bank — or of the country — is human, and thus vulnerable to human frailties. Thus our Constitution places us all in the care of an institution of laws that are (ideally) created with patience and reflection. Then those laws will, in turn, protect and defend us in times of peace or strife, but all while helping us to still maintain our sacred liberties.
And one of the most important protections our laws can provide is to protect us against the intrusions of our own government. That is where the critically important doctrine of habeas corpus comes into play.
Habeas corpus in Latin literally means "You are to hold (or arrest) the body." So a writ of habeas corpus is a challenge in court by the person who is being imprisoned. It has also been expanded to cover the type of imprisonment, or even the threat of imprisonment, as well as the custody of a minor child.