The following are two important philosophers that influenced Thomas Jefferson's writing of the Declaration of Independence:
1) John Locke- Locke wrote a famous book Two Treaties of Government. In this book, he discussed several different topics including the idea of unalienable rights. This refers to a set of rights that all individuals have just because they are human. Jefferson refers to this idea when he talks about how all men have the right to "life, liberty, and pursuit of happiness."
2) Thomas Hobbes- Jefferson's indirect reference to the idea of a social contract was inspired by the work of Thomas Hobbes.