That which is particular to an experience, and cannot be communicated. It is sometimes thought that the precise feels of particular qualia of experience are ineffable. The other examples of philosophical interest are the states of mind achieved in mystical ecstasy, which are often felt to be especially revelatory of the true nature of the world, but also incommunicable. However the notion of an incommunicable content is commonly regarded with grave suspicion, on the grounds that genuine content involves the recognition of something; that this requires the application of rules; but rules must be public and communicable. See also private language argument, rule-following considerations.