The rhetorical device demonstrated by the expression "keeping a car and paranoia between them" is syllepsis. Syllepsis is one of the many rhetorical devices that are Figures of Division. Syllepsis is a figure of division that describes syntactical or semantic divisions within a clause or sentence. The other device in this type of figures of division is the zeguma (similar to syllepsis though not synonymous).
The various types of figures of division are used as methods of amplification, as Amplificato. Figures of division amplify, or enlarge upon, the message being communicated through one or more means. Syllepsis and zeguma do this by dividing the expected syntax or semantic meaning in order to foreground (or call attention to) a special new meaning. Syllepsis and zeguma (both the same type of figure of division) each use a single word to govern other words in a sentence. The division they create either affects other parts of speech (zeguma) or other word meanings (syllepsis); both devices are appropriate to only one application in the sentence.
- Zeguma: Neither Mar's sword nor war's fire shall burn ("shall burn" is appropriate to "war's fire," which shall be prevented from igniting)
- Syllepsis: Keeping a car and paranoia between them ("keeping something between them" is appropriate to only a car; paranoia is an abstract that cannot be "kept between them")
Syllepsis is defined as a figure of division that amplifies syntactical structure or semantic meaning by using one word with two or more others when only one of the other words can appropriately be governed by the single one because it must be understood differently in relation to each of the other words.
In "keeping a car and paranoia between them," the phrase keeping something between them is understood in physical and spacial terms when referring to a car, which is a physical object that can occupy space between two other physical objects. The phrase is understood in metaphorical or confidential terms when referring to paranoia since paranoia is a psychological disorder of perception and of the mind, which can be used in a metaphorical sense.