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
Mr. Cogito whose presence is introduced by a poem entitled "Dusza Pana Cogito" (Mr. Cogito's Soul). It brings to our attention Mr Cogito's soul leading a life of its own. In contrast with the souls of the ancient world, it tends to leave him unexpectedly, wandering here and there, oblivious of the owner's well-being. The soul always returns, though, making it possible for Mr. Cogito to adore the world's beauty and diversity in the next poem – "Modlitwa Pana Cogito – podróżnika" ("A Prayer Of Mr. Cogito The Traveller"). This is followed by "Pan Cogito – powrót" ("Mr. Cogito – A Return"),