One of my favorite political theorists is Algernon Sidney (1623-1683). Sidney’s most famous work is Discourses Concerning Government (1698, published posthumously because Sidney had been executed for treason by Charles II). In addition to his motivation to write in response to the absolutism and authoritarianism of both Oliver Cromwell (whom he considered a tyrant) and the Stuart kings of England, Sidney wrote against absolutism and the divine right of kings in response to Robert Filmer, a pro-monarchy theorist. According to Wikipedia (and this summary accords with my understanding):
For Sidney absolute monarchy, in the form practiced by Louis XIV, was a great political evil. His Discourses Concerning Government (the text for which Sidney lost his life) was written during the Exclusion Crisis, as a response to Robert Filmer‘s Patriarcha, a defence of divine right monarchy, first published in 1680. Sidney was quite opposed to the principles espoused by Filmer and believed that the Sovereign’s subjects had the right and duty to share in the government of the Realm by giving advice and counsel. It was Filmer’s business, he wrote, “to overthrow liberty and truth.” Patriarchial government was not ‘God’s will’, as Filmer and others contended, because the “Civil powers are purely human ordinances.”
Chapter 3 of Discourses contains important parts of Sidney’s argument, and shows his application of classical Roman political theory to argue for a republican form of government grounded in the participation and power of the governed. In it Sidney says that
That which is not just, is not Law; and that which is not Law, ought not to be obeyed.
You may think that Sidney’s arguments have a lot in common with John Locke’s, and you’d be correct. But Sidney goes even further than Locke. Locke argued that those living under a despotic or tyrannical government, living under illegitimate power, have the right to revolt against that government because the power of the government derives from the individuals in the society. Sidney says that not only do those living under illegitimate political power have the right to revolt against that government, but that people living under illegitimate power have a moral duty to revolt against that government.
Sidney was second only to Locke in influence among the American founders and those who forged the institutions of the United States and who put forward the arguments for rebellion against the British government.