This postcard is from my small collection. It appears to be franked 1908. This would fit with the 10 centimes stamp for this was the cost of sending a postcard within France between 1878 to 1917.
Descartes itself is a commune of l’ Indre-et-Loire/Touraine. It initially had the latin name Haya which later became La-Haye and then La Haye-Descartes in 1802. When the town amalgamated with the village of Balesmes in 1966 the new commune was named Descartes to commemorate Rene Descartes who was born in La Haye.
A short history of the town of Descartes may he found here.