"Goodbye," said the fox. "That's my secret. It 'very simple: One sees clearly only with the heart. L 'essential is invisible to the eye "(Cap.XXI)
We are in the middle of the Cap. XXI of the book "The Little Prince" by Antoine de Saint-Exupery (Lyon, June 29, 1900 - Mar Tirreno, 31 July 1944), and which in the following will simply call Antoine. (Author's note. Ble in the text corresponds to the original book).