In a 1927 letter to Sigmund Freud, Romain Rolland coined the phrase 'oceanic feeling' to refer to a sensation of 'eternity', a feeling of 'being one with the external world as a whole', inspired by the example of Ramakrishna, among other mystics. According to Rolland, this feeling is the source of all the religious energy that permeates in various religious systems, and one may justifiably call oneself religious on the basis of this oceanic feeling alone, even if one renounces every belief and every illusion.