“Show (them), don’t tell (them)” is a popular adage told to writers of all kinds, but especially drama scriptwriters. The audience must learn about a character through action and events, not simply by a character talking away at great length. The saying “show them, don’t tell them” has been cited in print since at least 1963.
 
“Show, don’t tell” was credited in a 1971 book (see below) to Theodore Morrison, a Harvard creative writing and English professor from 1931-1963 and a director of the annual Breadloaf Writers’ Conference at Middlebury College from 1932-1955. This has not been confirmed by an earlier citation.
 
   
Wikipedia: Show, don’t tell
Show, don’t tell is a technique often employed by writers to enable the reader to experience the story through action, words, thoughts, senses, and feelings rather than through the author’s exposition, summarization, and description. The goal is not to drown the reader in heavy-handed adjectives, but rather to allow readers to experience the author’s ideas by interpreting significant, well-chosen textual details. The technique applies equally to fiction and nonfiction.
 
Google Books
Verdi:
His Music, Life, and Times
By George Whitney Martin
New York, NY: Dodd, Mead
1963
Pg. 242:
The first rule of dramatic writing, whether for opera or play, can be stated simply as: ‘Show them; don’t tell them.’ For violating this first rule Verdi and Cammarano had to pay still another penalty.
 
Google Books
The Writing of Novels
By Christopher Derrick
Boston, MA: The Writer, Inc.
1969
Pg. 172:
The old rule, therefore, still holds good: show, don’t tell. There’s no reason for us to believe what you say: you have come before us as a writer of fictions, a liar. But let the thing seem to happen before our eyes, and you’ll have us hooked and credulous.
   
Google Books
The Mass Media Book
By Rod Holmgren and William Norten
Englewood Cliffs, NJ: Prentice-Hall
1971
Pg. 159:
One of the basic rules that Prof. Theodore Morrison drills into his creative writing students at Harvard is, “Show, don’t tell.”
   
Google Books
The Wrought Response;
Reading and writing about literature
By Ray Kytle and Juanita Lyons
Encino, CA: Dickenson Pub. Co.
1972
Pg. 146:
Show, don’t tell. Images show There’s an old creative writing course bromide that goes “Show, don’t tell.” Another way to say it is: “Imply, don’t state.”
 
Google Books
Forming, Thinking, Writing:
The Composing Imagination
By Ann E. Berthoff
Montclair, NJ: Boynton/Cook
1983, ©1982
Pg. 121:
What is generally meant by “Show, don’t tell” is something like this: “Don’t go on and on writing statements that are all conceptual; don’t depend on dictionary definitions; show your reader the examples from which you have generalized.”
 
OCLC WorldCat record
Show, don’t tell : District writing project.
Author: Salt Lake City Writing Project.; Salt Lake City School District.
Publisher: [Salt Lake City, Utah] : Salt Lake City Schools, 1986.
Edition/Format:  Book : English
 
Google Books
How to Write a Movie in 21 Days:
The Inner Movie Method
By Viki King
New York, NY: Perennial Library
1988
Pg. 117:
How well are you laying in exposition? Are you having the character say, “This is my birthday and it’s the Depression and I’m an orphan”? Show, don’t tell.
 
OCLC WorldCat record
Show, don’t tell : a writer’s guide
Author: William Noble
Publisher: Middlebury, Vt. : P.S. Eriksson, ©1991.
Edition/Format:  Book : English
 
OCLC WorldCat record
Specificity and imagery in writing: Testing the effects of show, don’t tell
Author: J Tankard; L Hendrickson
Edition/Format:  Article : English
Publication: NEWSPAPER RESEARCH JOURNAL, 17, no. 1/2, (1996): 35-48
Database: British Library Serials
   
Google Books
Writing Short Scripts (2nd edition)
By William H. Phillips
Syracuse, NY: Syracuse University Press
1999
Pg. 12:
Second, show, don’t tell. Don’t, for instance, explain that what you write is funny or sad; write in such a way that the entry is funny or sad.
 
OCLC WorldCat record
Advanced screenwriting : raising your script to the Academy Award level
Author: Linda Seger
Publisher: Los Angeles : Silman-James Press, ©2003.
Edition/Format:  Book : English : 1st ed
Contents:
(...)
Show, don’t tell
 
OCLC WorldCat record
The only writing series you’ll ever need : screenwriting : insider tips and techniques to write for the silver screen!
Author: Madeline DiMaggio
Publisher: Avon, Mass. : Adams Media, ©2007.
Series: Only writing series you’ll ever need. 
Edition/Format:  Book : English
Contents:
(...)
A Different Type of Game: Show, Don’t Tell
 
OCLC WorldCat record
Drama! Show, don’t tell.
Author: Paul Ruditis
Publisher: Simon Pulse, 2008.
Series: Drama!, bk. 3. 
Edition/Format:  Book : English
   
OCLC WorldCat record
Screenwriter’s Compass : Character As True North.
Author: Guy Gallo
Publisher: Burlington : Elsevier Science, 2012.
Edition/Format:  eBook : Document : English
Contents:
(...)
Show, Don’t Tell