Metaphor and metonymy :

The extract is taken from "Nice Work" by David Lodge, a very postmodern text.  It records a conversation between Vic Wilcox and Robyn Penrose about the main different between metaphor and metonymy. Indeed, they have an argue about an
advertisement they noticed every few miles they passed. There was no words on it, but just a cigarettes image called "Silk Cut". In this way, they wonder  why a pack of cigarettes is called in this way. Being Robyn a postmodern character, she looks for a content hidden beneath this simple image.  

In line with postmodernist era, the aim of the text is to entertain the reader creating expectation and, at the same time, to make explicit the different function between metaphor and metonymy in communication.
 

Metaphor is a figure of speech based on similarity,used when you substitute something like the thing you mean for the thing
itself. In this case, the word "Silk" makes an intelligent reader able to think about its strange use. Silk, in fact, with its curves and sensuous texture  symbolized the female body and the elliptical slit is like a vagina. All that takes the reader to have both sensual and sadistic impulses.

The conversation between Robyn and Vic continues in two binary system. Robyn tries to find hidden meanings in things while Vic wonders why she does it.  

In addition, Robyn explains to Vic what the word metonymy means. It substitutes some attribute or cause or effect of the thing
for the thing itself. She is a postmodern woman because she knows everything about language and how it works. She gives an example of it describing how Sigmund Freud analyses how dreams work.

In conclusion, reader's reactions are absolutely entertaining in line with the aim of David Lodge. The text makes the reader laugh because of the way is written and also of the way Vic is characterized. Vic is different from Robyn because he won't know nothing and he doesn't want to find an hidden meaning in what he sees. This is a Postmodernism's technique  in which a character, or a meaning, is portrayed by a difference.