Oceanic feeling is a psychological term coined by Romain Rolland and popularized by Sigmund Freud in his books The Future of an Illusion (1927) and Civilization and Its Discontents (1929/1930) to criticize the psychological feeling of religion, the "oceanic" feeling of limitlessness. According to Rolland's definition of the term, this feeling is the source of all religious energy which permeates in various religious systems. It is a sensation of an indissoluble bond, as of being connected with the external world in its integral form. This feeling is an entirely subjective fact and is not an article of faith. Rolland's view is that one may justifiably call oneself religious on the basis of this oceanic feeling alone, regardless if the adherent renounces every belief and every illusion. On the other hand, Freud cannot sympathize with such feeling since he admits he cannot find it in himself. It is not easy, he says, to analyze emotions scientifically. To Freud, this feeling is a fragment of infantile consciousness when the infant begins to differentiate himself from his human and non-human environment. In his opinion, there is not a strong enough need for it to be the source of all religious energy. Freud does not deny that this feeling may occur in people and offers a psychoanalytical explanation.
The concept was coined in a letter of December 5th, 1927 from Rolland to Freud as part of their correspondence, where Rolland writes:
Mais j'aurais aimé à vous voir faire l'analyse du sentiment religieux spontané ou, plus exactement, de la sensation religieuse qui est (...) le fait simple et direct de la sensation de l'éternel (qui peut très bien n'être pas éternel, mais simplement sans bornes perceptibles, et comme océanique).—
In strict translation:
But I would have liked to see you make an analysis of the spontaneous religious sentiment or, more exactly, of the religious sensation which is (...) the simple and direct fact of the sensation of the eternal (which can very well not be eternal, but simply without perceptible boundaries, and like oceanic). Similar as an independent contact, the feeling is fundamentally subjective. 
Freud ends The Future of An Illusion with a discussion of the concept, and picks up the discussion as the beginning of Civilization and Its Discontents, answering Rolland's request. In Civilization, Freud credits the concept to an anonymous friend, referring to Rolland.
Rolland originated the concept based on his studies of Eastern mysticism.
Freud related the Oceanic feeling to Narcissistic elation.
Freud argues that the "oceanic feeling", if it exists, is the preserved "primitive ego-feeling" from infancy. The primitive ego-feeling precedes the creation of the ego and exists up until the mother ceases breastfeeding. Prior to this, the infant is regularly breastfed in response to its crying and has no concept that the breast does not belong to it. Therefore, the infant has no concept of a "self" or, rather, considers the breast to be part of itself. Freud argues that those experiencing an oceanic feeling as an adult are actually experiencing a preserved primitive ego-feeling. The ego, in contrast, comes into existence when the breast is taken away, and involves the infant's recognition that it is separate from the mother's breast, and therefore, that other persons exist. Freud argues that it would not necessarily contradict psychoanalytical theory for this primary ego-feeling to coexist along with the ego in some people. The main argument for this is that psychoanalytical theory holds that all thoughts are preserved in a conservation of psychic energy. Therefore, the "oceanic feeling" described as a oneness with the world or a limitlessness is simply a description of the feeling the infant has before it learns there are other persons in the world.
"Neurotheology" is a neologism that describes the scientific study of the neural correlates of religious or spiritual beliefs and practices. Other researchers have rejected the term, preferring to use terms like "spiritual neuroscience" or "neuroscience of religion". Researchers in the field attempt to explain the neurological basis for religious experiences, such as:
- The perception that time, fear or self-consciousness have dissolved
- Spiritual awe
- Oneness with the universe
- Ecstatic trance
- Sudden enlightenment
- Altered states of consciousness
- Emotions in the Christian Tradition (Stanford Encyclopedia of Philosophy) http://plato.stanford.edu/entries/emotion-Christian-tradition/
- The Ontology of Religiosity: The Oceanic Feeling and the Value of the Lived Experience
- Freud, Sigmund. Civilization and its Discontents. pps 11-13 http://ia340931.us.archive.org/0/items/CivilizationAndItsDiscontents/freud_civilization_and_its_discontents.pdf
- Un beau visage à tous sens. Choix de lettres de Romain Rolland (1866-1944), Paris, Albin Michel, 1967, pp. 264–266. (French)
- Vermorel, Henri, and Vermorel, Madeleine, eds. (1993). Sigmund Freud et Rolland Romain. Correspondance 1923-1936. Paris: Presses Universitaires de France.
- Burton, Robert A. (2008). "Neurotheology". On Being Certain. Believing You Are Right Even When You're Not. New York City: Macmillan Publishers/St. Martin's Press. ISBN 1-429-92611-2; ISBN 978-14-2992-611-9 (Macmillan Publishers edition). ISBN 0-312-35920-9; ISBN 978-03-1235-920-1 (St. Martin's Press edition).