Of the ends of society and government

The great and chief end of men uniting into commonwealths and putting 
themselves under government is the preservation of their property. To 
which in the state of nature there are many things wanting:

First there wants an established, settled, known law, received and 
allowed by common consent to be the standard of right and wrong and to 
the common measure to decide all controversies between them; for though 
the law of nature be plain and intelligible to all rational creatures, 
yet men, being biased by their interest as well as ignorant for want of 
studying it, are not apt to allow of it as a law binding to them in the 
application of it to their particular cases.

Secondly, in the state of nature there wants a known and indifferent 
judge with authority to determine all differences according to the esta-
blished law; for every one in that state being both judge and executioner 
of the law of nature, men being partial to themselves; passion and 
revenge is very apt to carry them too far and with too much heat in their 
own cases, as well as negligence and unconcernedness to make them too 
remiss in other men's.

Thirdly, in the state of nature, there often wants power to back and 
support the sentence when right, and to give it due execution. They who 
by any injustice offend will seldom fail, where they are able, by force, 
to make good their injustice; such resistance many times makes the 
punishment dangerous and frequently destructive to those who attempt it.

from John Locke - Two treatises of Government