Meditations on First Philosophy is a philosophical treatise by René Descartes first published in 1641. The book is made up of six meditations, in which Descartes first discards all belief in things that are not absolutely certain, and then tries to establish what can be known for sure. He wrote the meditations as if he had meditated for six days: each meditation refers to the last one as yesterday. (In fact, Descartes began work on the Meditations in 1639.) One of the most influential philosophical texts ever written, it is widely read to this day.