Any rational expression, reason.
Expression in words, either speech or writing.
A formal lengthy exposition of some subject, either spoken or written.
An institutionalized way of thinking, a social boundary defining what can be said about a specific topic (after Michel Foucault).
To exercise reason; to employ the mind in judging and inferring; to reason.
To engage in discussion or conversation; to converse.
To write or speak formally and at length.
Reason for being. The claimed reason for the existence of something or someone; the sole or ultimate purpose of something or someone.