Although not actually a character in this book, Locke himself is one of the most important philosophers in history. His work, especially this book and his Two Treatises of Government, was wildly influential. Although this particular work is not studied anymore as much as later work by David Hume, it was extremely influential in its day and one reason that it is not studied as much as one might think is that the work is both incredibly radical and so widely responded to by both critics and supporters that the substance of Locke's ideas were integrated into later thinkers.