Language is Understanding
From 'A Study of Our Decline' by P Atkinson (October 2009)

"What a man cannot state he does not perfectly know, and conversely the inability to put his thoughts into words sets a boundary to his thought … English is not merely the medium of our thought; it is the very stuff and process of it." — Report of the Departmental Committee on the Teaching of English in England; H. M. Stationery Office (1921)

A man may have a notion but the only way of determining the value of such an impression is to express it in words, and then, and only then, can he grasp the substance of the idea. And if an author omits this step, the risk is that the idea will not be rational but fanciful. So not even the author knows what an idea is until it is clearly expressed in words, a quality which makes language the essence of understanding. Diagrams and pictures may be used to support words, but it is the words that contain the idea. (see also) Hence:

— which is why all English speaking citizens should strive to use plain English in their thoughts as well as their communications.

Nevertheless, language is merely a discipline where meaning is created by the universal adoption of the rules of spelling and grammar. So:

Hence the crucial importance of mastery of the use of language, both to the individual and to the community. And the only way such mastery can be maintained is by regular exercise; that is by frequent discussion, reading, writing or speeches. Otherwise not only will the mastery of language decay, but also understanding.

Language is also tradition, for it is tradition that establishes the words, spelling and grammar; hence it is tradition that forms the basis of communal understanding, so the corruption of tradition is the corruption of communal understanding.