Why might parliament have included the point that its members should be elected freely? what larger concept is supported by this point?

Free elections did not become customary in the world until the development of the idea of representative democracy around the 17th and 18th century.

Greek democracy was a direct form, which meant that citizens voted for the policies directly, instead of voting for people to vote on the policies. The Roman Republic, on the other hand, had some quasi-representative aspects. The way that democracy was instituted in the US resembles the Roman system more than the Greek one.

The purpose of a representative democracy is to try to take into account the opinions of huge, complex populations in the decision-making process. Because of the size of most modern nations, it would be extremely difficult, if not outright impossible, to establish a direct democracy. Therefore, representation is the best way to allow everyone to have a voice in government.

The free election of representatives, on the other hand, is protected by secret ballots and by laws that ensure the protection of privacy when voting. Its introduction points towards the idea of equal and fair representation and of the power of the state residing with the people.

This system, along with the laws that protect it, ensures that ideas that are vital to democracy, such as universal suffrage and free election, are maintained in our elections.

so they can defeat there oppenent

social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they live