a generalization of all these concepts [metaphor, deepity, motte and bailey]:

Blurry sentence: a sentence with at least two possible interpretations, where one is both much more interesting and much less plausible than the other. The effect is to make the reader feel that the sentence is both interesting and plausible. The implausible interpretation also does not help the reader to understand the plausible one.

Here’s how the generalization works:

Basic metaphor: a blurry sentence where the plausible interpretation is the most salient one to the reader.

Deepity: a blurry sentence where neither the plausible interpretation nor the implausible interpretation is much more salient than the other, leaving the reader with a sense of vagueness or ineffability. The feeling is: There is something true and interesting here, although I can’t quite put my finger on it.

Motte and bailey: a blurry sentence where the implausible interpretation is the most salient one. If the reader objects that the sentence is in fact implausible, then the writer has the option of switching to only the plausible interpretation.

These revised definitions reveal that there is a spectrum here, such that the names “basic metaphor,” “deepity,” and “motte and bailey” are only calling out particular regions of the spectrum.

Ben Garfinkel, Basic Metaphors, Deepities, and Motte-and-Baileys, The best that can happen, 16 September 2017

Added to diary 15 January 2018