“A dead language is not only one no longer spoken or written, it is unyielding language content to admire its own paralysis. Like statist language, censored and censoring.”

"Common Places," No. 13, The Literary Examiner (September - December 1823)

"Come Back, Dizzy" (p.187)
So This Is Depravity (1980)

Source: How Language Works, 2007, p. 2

Source: How Language Works, 2007, p. 357
Context: However language began, one thing is certain – it immediately began to change, and has been changing ever since. Languages are always in a state of flux. Change affects the way people speak as inevitably as it does any other area of human life. Language purists do not welcome it, but they can do very little about it. Language would stand still only if society did. A world of unchanging linguistic excellence, based on the brilliance of earlier literary forms, exists only in fantasy. The only languages that do not change are dead ones.

Source: 1960-70's, Prospectus et tous écrits suivants, 1967, p. 94

Source: Die Mathematik die Fackelträgerin einer neuen Zeit (Stuttgart, 1889), p. 5.

Answer to a survey written by the French mathematician Jaques Hadamard, from Hadamard's An Essay on the Psychology of Invention in the Mathematical Field (1945). Reprinted in Ideas and Opinions (1954). His full set of answers to the questions can be read on p. 3 here http://www.pitt.edu/~jdnorton/Goodies/Einstein_think/index.html.
1940s
Context: The words or the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thoughts are certain signs and more or less clear images which can be "voluntarily" reproduced and combined. There is, of course, a certain connection between those elements and relevant logical concepts. It is also clear that the desire to arrive finally at logically connected concepts is the emotional basis of this rather vague play with the above-mentioned elements.... The above-mentioned elements are, in my case, of visual and some muscular type. Conventional words or other signs have to be sought for laboriously only in a secondary stage, when the mentioned associative play is sufficiently established and can be reproduced at will.

The Paris Review interview (1984)
Context: Beckett shows death; his people are in dustbins or waiting for God. (Beckett will be cross with me for mentioning God, but never mind.) Similarly, in my play The New Tenant, there is no speech, or rather, the speeches are given to the Janitor. The Tenant just suffocates beneath proliferating furniture and objects — which is a symbol of death. There were no longer words being spoken, but images being visualized. We achieved it above all by the dislocation of language. … Beckett destroys language with silence. I do it with too much language, with characters talking at random, and by inventing words.

Butterfly Boy: Memories of a Chicano Mariposa (2006)