David Hume (1711-1776) was no hardcore libertarian, but he was a provocative thinker and a key figure in the development of liberalism. Hume helped make the Scottish Enlightenment the important period it was. He also can be fun to read. Observe this from his essay “Of the Independency of Parliament”:Read it all here.
Political writers have established it as a maxim, that, in contriving any system of government, and fixing the several checks and controuls of the constitution, every man ought to be supposed a knave, and to have no other end, in all his actions, than private interest. By this interest we must govern him, and, by means of it, make him, notwithstanding his insatiable avarice and ambition, co-operate to public good. Without this, say they, we shall in vain boast of the advantages of any constitution, and shall find, in the end, that we have no security for our liberties or possessions, except the good-will of our rulers; that is, we shall have no security at all.