Age of Enlightenment Louis XV until the French Revolution. If taken back to the mid-17th century, the Enlightenment would trace its origins to Descartes' "Discourse on the Method", published in 1637. In France, many cited the publication of Isaac Newton's "Principia Mathematica" in 1687. It is argued by several historians and philosophers that the beginning of the Enlightenment is when Descartes shifted the epistemological basis from external authority to internal certainty by his "cogito ergo sum" published in 1637. As to its end, most scholars use the last years of the century, often choosing the French Revolution of 1789 or the beginning of
Cogito, ergo sum and let him deceive me as much as he can, he will never bring it about that I am nothing, so long as I think that I am something. So, after considering everything very thoroughly, I must finally conclude that the proposition, "I am, I exist," is necessarily true whenever it is put forward by me or conceived in my mind. (AT VII 25; CSM II 16–17) There are three important notes to keep in mind here. First, he claims only the certainty of "his own" existence from the first-person point of view — he has not proved the existence