Which enlightenment phliosopher introduced the idea that people enter a social contract with the purpose of maintaining order in society?

The idea belongs to 18th-century  French thinker Jean-Jacques Rousseau. He discussed it in his book The Social Contract. Rousseau argued against the divine right of monarchs to rule, and he stated that the people are the sovereign. All should enjoy the same rights and the same duties, he argued. All members of society must give their consent to laws governing them in the social contract. We submit our individual will to a collective will created of men born free and equal.  This collective will will be directed at the common good. This is how order can be maintained.

Explanation:

d) in the state of iowa