Thomas Hobbes

The Englishman who wrote political theory out of fear, and was honest about it. Living through civil war, he concluded that life without a strong common power was a war of all against all, and that almost any order was better than that. Leviathan is the starting gun for modern political thought. Nearly everyone who came after, including those who despised his conclusions, had to argue against him first. That is the mark of a foundational book.