Half-truth
A statement that is literally true but leaves out the part that would change what the audience concludes from it.
The half-truth is the safest lie. Every word can be defended; the deception lives in the space after the full stop. "The car has never had an accident" is true of a car whose engine is failing; "the treatment is approved" is true of a treatment approved for a different condition. The audience assumes that a speaker who volunteers a fact has volunteered the relevant ones, and the device exploits that assumption.
Sissela Bok's study of lying distinguishes deception from falsehood: one can deceive with true statements, and the half-truth is the standard way. It differs from card stacking in scale, one statement rather than a case, and from paltering, which is a half-truth offered in direct answer to a question. Exploits Anchoring and the assumption of cooperative communication.
Historical examples
The Pentagon Papers, the Defense Department's own history of the war published in 1971, set official public statements of progress beside the internal assessments made at the same time. The public statements were rarely false; they reported the gains and left out the estimates that the gains would not hold. The gap between the two was the story.
Sheehan, Neil, et al. The Pentagon Papers as Published by The New York Times. New York: Bantam, 1971; Ellsberg, Daniel. Secrets: A Memoir of Vietnam and the Pentagon Papers. New York: Viking, 2002.
Bok's Lying: Moral Choice in Public and Private Life set out why true statements can deceive and why the half-truth is the deceiver's preferred instrument: it preserves the speaker's claim to honesty while producing the false belief. The book's examples run from medicine to government and remain the standard treatment.
Bok, Sissela. Lying: Moral Choice in Public and Private Life. New York: Pantheon, 1978.
In advertising and commerce
"0% interest" is true for the introductory period; "no annual fee" is true of the card, not the transactions; "free" is true until the trial converts. Consumer-protection rules on "material omissions" exist because the industry's most reliable statements were the true ones with something left out.
Federal Trade Commission. Policy Statement on Deception, 14 October 1983 (appended to Cliffdale Associates, 103 F.T.C. 110), on material omissions.
Find a claim that is true. Write the question it answers. Then write the question a buyer or voter would actually want answered. Are they the same?
In the wild
Short examples of the technique at work, each with what to notice. The same examples are questions in the quiz, where the answer is not given away.
"This car has never failed an emissions test." It has never been tested.
What to notice. True, and the missing fact reverses what the buyer concludes.
"The plant has had no reportable incidents this year." The reporting threshold was raised in January.
What to notice. The scope word "reportable" carries the omission; the statement is true only because of it.
"Our supplement is approved for sale." Approval for sale means it was not shown to be effective.
What to notice. A reassuring fact that answers a question about safety filing, offered as if it answered one about effect.
Sources
- Bok, Sissela. Lying: Moral Choice in Public and Private Life. New York: Pantheon, 1978. ISBN 978-0375705281
- Ellsberg, Daniel. Secrets: A Memoir of Vietnam and the Pentagon Papers. New York: Viking, 2002. ISBN 978-0142003428
- Federal Trade Commission. Policy Statement on Deception, 1983.
- Grice, H. P. "Logic and Conversation." In Syntax and Semantics, vol. 3, edited by P. Cole and J. Morgan, 41–58. New York: Academic Press, 1975.