RATIO. The essence or nature of something intelligible to the mind. It is therefore the intelligibility of any essence. In ecclesiastical language it is the ground or reason or rationale of a thing, especially as pertaining to an organized body of knowledge, legislation, or method of performing an activity. Thus the Code of Canon Law has a fundamental ratio or set of principles on which it is based. (Etym. Latin ratio, reason; intelligence, mind, act of reasoning, knowledge, plan, motive, argumentation, account.)