The significance of the Magna Carta in the development of political thought lies in its establishment of the principle that everyone, including the monarchy, is subject to the law. Signed in 1215, it served as a crucial turning point in limiting arbitrary power and protecting individual rights. The Magna Carta introduced ideas such as due process and the right to a fair trial, which would later influence democratic ideals and constitutional frameworks in various countries. It is often regarded as a foundational document for principles like rule of law and limited government.