The main purpose of each of these excerpts is to declare the intentions of the writers and their purpose for writing.
In the Magna Carta, the intention is to affirm the rights of the English Church and establish a framework for governance based on respect for these rights. In the Declaration of the Rights of Man, the intention is to set forth the natural, unalienable rights of man and to outline the responsibilities of the government to protect these rights, reflecting the aspirations of the National Assembly. Both documents emphasize establishing a clear purpose and framework for their respective rights and governance.