A hypothetical society filled with people similar to the one you describe (one who adheres to no moral code or philosophy other than survival and satisfaction of his 'gut'), would be literal case of "he who has the most power makes the rules and decides what is right and what is wrong." People would be held in check mainly through fear of negative consequences carried out by more powerful men. They would obey the rules simply because they get more advantage out of obeying them than disobeying them.
The best literary examples that Teary can think of would be:
"The Sea Wolf" by Jack London
and
"The Abolition of Man" by C.S. Lewis.
both really good reads.