The beginning of the Age of Enlightenment in Europe is often marked by the publication of Isaac Newton's work, particularly the Principia Mathematica in 1687. Newton's ideas about gravity and the laws of motion challenged prevailing thought and emphasized the importance of reason and empirical evidence. The Enlightenment was characterized by a shift towards rationalism and individualism, as thinkers like Voltaire and Rousseau further developed concepts of liberty, democracy, and human rights, shaping modern Western philosophy.