Age of Enlightenment, though several historians and philosophers argue that it was marked by Descartes' 1637 philosophy of Cogito, ergo sum ("I think, therefore I am"), which shifted the epistemological basis from external authority to internal certainty. In France, many cited the publication of Newton's Principia Mathematica (1687), which built upon the work of earlier scientists and formulated the laws of motion and universal gravitation. The middle of the 17th century (1650) or the beginning of the 18th century (1701) are often used as epochs. French historians usually place the Siècle des Lumières ("Century of Enlightenments") between 1715 and 1789: from the beginning of the reign of Louis XV until the French Revolution. Most scholars use the last years of the century, often choosing the French Revolution or the beginning of the Napoleonic Wars (1804) as a convenient point in time with which to date the end of the Enlightenment. In recent years, scholars have expanded the time span and global perspective of the Enlightenment by examining: (1) how European intellectuals did not work alone and other people helped spread and adapt Enlightenment ideas, (2) how Enlightenment ideas were "a response to cross-border interaction and global integration", and (3) how the Enlightenment "continued throughout the nineteenth century and beyond." The Enlightenment "was not merely a history of diffusion" and "was the work of historical actors around the world... who invoked the term... for their own specific purposes." Modern study In the 1947 book Dialectic of Enlightenment, Frankfurt School philosophers Max Horkheimer and Theodor W. Adorno argue: Extending Horkheimer and Adorno's argument, intellectual historian Jason Josephson Storm argues that any idea of the Age of Enlightenment as a clearly defined period that is separate from the earlier Renaissance and later Romanticism or Counter-Enlightenment constitutes a myth. Storm points out that there are vastly different and mutually contradictory periodizations of the Enlightenment depending on nation, field of study, and school of thought; that the term and category of "Enlightenment" referring to the Scientific Revolution was actually applied after the fact; that the Enlightenment did not see an increase in disenchantment or the dominance of the mechanistic worldview; and that a blur in the early modern ideas of the humanities and natural sciences makes it hard to circumscribe a Scientific Revolution. Storm defends his categorization of the Enlightenment as "myth" by noting the regulative role ideas of a period of Enlightenment and disenchantment