At American Creation Tom Van Dyke has two must read posts on how to properly understand John Locke. Indeed Thomas Jefferson identified "Aristotle, Cicero, Locke, Sidney, &c. .." as the chief ideological sources behind the Declaration of Independence.
Most of us realize that John Locke's philosophy was central to the US Founding. So we go back and venerate him and turn him into a larger than like figure. The irony that few appreciate is that Locke was anything but venerated by his Christian contemporaries of the day. He published his most notable works anonymously and had to flee England for the Continent because his life was in danger. As such Locke treaded with great caution as he exposited his ideas.
Algernon Sidney, another of Jefferson's Whig sources, wasn't cautious enough. As Van Dyke puts it:
Locke's contemporary, Algernon Sidney, argued along the same lines as Locke, for liberty and against the "divine right of kings." Sidney got his neck stretched by the English crown in 1683 for his outspokenness. Since there was only one witness against Sidney in his A Man for All Seasons-type tribunal but the law required two, the second witness called was Sidney's Discourses upon Government, a book that was much admired by the American Founders, but which proved fatal to its author. Aaaaaaaaaa-ack!
John Locke was not so naïve as poor Algernon Sidney as to the ways of man and his governments. If you want to die in bed, keep a low profile and tell the truth not at the top of your lungs, but sotto voce.
This well illustrates the difference between "common law" principles on the one hand and "Whig" on the other. Common law principles were those common "rights of Englishmen" that were very traditional and had been evolving for hundreds of years. "Whig" principles, on the other hand, were much more radical, revolutionary, dissident, and pro-political liberty. For instance jurist William Blackstone, the most notable "common law" source, was a Tory and against the American side in the Revolution.
Those were two of five sources that Harvard Historian Bernard Bailyn identifies as making up the ideology of the American Founding. The other three were Christian principles, Greco-Roman principles, and Enlightenment principles. Not all of these sources were "mutually exclusive." One could argue that Locke represented "Christian," "Whig," and "Enlightenment" all three at the same time. Enlightenment and Whig were key in my humble opinion.