PNolan, "believe" is an an action:  "accept (something) as true; feel sure of the truth of".  It is not the knowledge, invented or not, that is believed in, it is the action of the person who believes.  And that action reflects upon character and nature of the person believing.   You have a system of beliefs, based upon observations, experiences, and information you have been provided by sources such as other people and books.   That you would believe that law enforcement would have originated in "slave patrols" indicates that your system of beliefs is not particularly connected to historical reality.   It is trivially easy to gain a better understanding:  https://en.wikipedia.org/wiki/Police#History