Ineffability is concerned with ideas that cannot or should not be expressed in spoken words (or language in general), often being in the form of a taboo or incomprehensible term. This property is commonly associated with philosophy, aspects of existence, and similar concepts that are inherently "too great", complex, or abstract to be adequately communicated. In addition, illogical statements, principles, reasons, and arguments may be considered intrinsically ineffable along with impossibilities, contradictions, and paradoxes. Terminology describing the nature of experience cannot be properly conveyed in dualisticsymbolic language; it is believed that this knowledge is only held by the individual from which it originates. Profanity and vulgarisms can easily and clearly be stated, but by those who believe they should not be said, they are considered ineffable. Thus, one method of describing something that is ineffable is by using apophasis, i.e. describing what it is not, rather than what it is. The architect Le Corbusier described his design for the interior of the Chapel of Notre Dame du Haut at Ronchamp as "l'espace indicible" translated to mean 'ineffable space', a spiritual experience which was difficult to describe.
"Tao can be told but any definition given is not perpetual; the name can be named but whatever name given is not perpetual." — Chapter One, Tao Te Ching
"My life, the most truthful one, is unrecognizable, extremely interior, and there is no single word that gives it meaning." — Clarice Lispector
T.S. Eliot's poem "The Naming of Cats" (1939) playfully suggests that every household cat must bear (besides whatever the family calls him) two additional names: one an exotic appellation shared by no other cat; the other forever unutterable because it is known only to the cat himself ("His ineffable effable / Effanineffable / Deep and inscrutable singular Name"). This idea is carried on in the movie "Logan's Run".
"Moses said to God, 'Suppose I go to the Israelites and say to them, "The God of your fathers has sent me to you," and they ask me, 'What is his name?' Then what shall I tell them?" God said to Moses, "I AM THAT I AM" — Exodus 3:13-14 (New International Version) (see Tetragrammaton).
"Of the subjects that concern me nothing is known, since there exists nothing in writing about them, nor will there ever exist anything in the future. People who write about such things know nothing; they do not even know themselves. For there is no way of putting these things in words like other things that one can learn. Hence, no one who possesses the true faculty of thinking (nous), and therefore knows the weakness of words, will ever risk framing thoughts in discourse, let alone fix them in so inflexible a form as that of written letters." — Hannah Arendt, paraphrase of PlatoSeventh Letter 341b-343a
"My philosophy...can no longer be communicated at least not in print." — Friedrich Nietzsche letter to Overbeck, July 2, 1885
"One no longer loves one's insight enough when one communicates it." — Friedrich Nietzsche, Beyond Good and Evil, No. 160
"The internal limit of all thinking...is that the thinker never can say what is most his own...because the spoken word receives its determination from the ineffable." Martin Heidegger, Nietzsche, Pfullingen , 1961, vol. II, p. 484
"The results of philosophy are the uncovering...of bumps that the intellect has got by running its head up against the limits of language." Ludwig WittgensteinPhilosophical Investigations, trans. G.E.M. Anscombe, New York, 1953, nos. 119.
"Philosophical problems arise when language goes on a holiday" (wenn die Sprache fetert). Ludwig WittgensteinPhilosophical Investigations, trans. G.E.M. Anscombe, New York, 1953, nos. 19
The nature of qualia (sensory experiences), such as colors or flavors (Although this has been challenged recently by research on ideasthesia finding that qualia are connected in semantic-like networks.)
The nature of emotions (with love being a prominent example)
Rape, particularly brutal examples of it associated with war.
Pope John Paul II proclaimed that abortion is "an unspeakable crime." He goes on to describe how a woman confronts the "profound sorrow and guilt" of a procured abortion, "the unspeakable horror of what [...] truly happened and [her] own responsibility for it every day and every night."