Why do laws exist?

Laws exist to protect the rights of the members of a
society and to ensure that they do not have to protect those rights through their own
actions.

Philosophers like John Locke argued that without
laws, human societies would be brutal places.  They argued that a society without laws
would be one in which individual people only had as many rights as they could protect. 
In other words, you only had the right to life if you could keep others from killing you
and you only had the right to your property if you could keep others from stealing
it.

Locke says that societies devised laws and governments
as a way to get themselves out of this state of nature.  The people would give up some
of their rights to the government.  In return, the government would protect their major
rights like life, liberty and property.

In this view, laws
exist in order to protect our most fundamental human rights.  Because we have laws and
ways to enforce them, we all have rights even if we would be too weak to protect those
rights in a state of nature.