Final answer:
The common idea in the Magna Carta, the Declaration of Independence, and the Declaration of Rights of Man and of the Citizen is the recognition and protection of individual rights and freedoms.
Step-by-step explanation:
The common idea that exists in the Magna Carta, the Declaration of Independence, and the Declaration of Rights of Man and of the Citizen is the recognition and protection of individual rights and freedoms. These founding documents emphasize the importance of life, liberty, and the pursuit of happiness as fundamental rights of all individuals. They also establish the principle that governments should derive their powers from the consent of the governed and that the people have the right to alter or abolish repressive forms of government.