Both concepts and Metaphor Systems are structured by picking out certain Dimensions of experience that form an Experiential Gestalt. Such gestalts help us when Coping With Experience.
Lakoff and Johnson, chapter 15.
"Conversation" is a concept. From an experience, we pick out certain Dimensions that are important to that concept:
* It involves speakers. * The speakers (roughly) take turns. * They have a rough pattern in time – introductory bits in the beginning, for example, likely recapitulation of some sort at the end. * One person stopping talking typically causes another person to start.
Conversation can now be used as the Source Domain of a metaphorical comparison provided enough of the Target Domain can be mapped onto the Source Domain properties. (See Family Resemblance.)
So we can speak of Heidegger being "in conversation" with Nietzsche even though they aren't taking turns talking.
See Conversation Becomes Argument for discussion of how a change in the experience can cause a new Source Domain to be applied. (See also Coping With Experience.)