The final group of key issues has to do with the relation between metaphor in language and metaphor in discourse. Discourse events concern the use of text in code in context, while language use involves the use of utterances in a specific language like English, Dutch, or Italian in a discourse event. These are two distinct levels of meaning making that have been described in Slowing metaphor down as involving first-order versus second-order semiotic modelling (inspired by the Russian-Estonian semiotician Yuri Lotman). This has at least four important consequences for deliberate and non-deliberate metaphor use as seen by DMT.
The structures and functions of metaphor at the level of language use, and their related psychological processes and products, boil down to the question whether the metaphor in question is used as a figurative comparison (analogy, cross-domain mapping) in the utterance or not. The issue becomes different when metaphor is seen as part of the discourse event that the utterance plays a role in: then the question arises whether the metaphor can also be attributed a purpose for the discourse event as an instance of text or talk. This has particular relevance for metaphor and framing.
A specific area where linguistic functions and discourse purposes of metaphor become quite explicit is metaphor in translation. When translators encounter metaphor in their source texts, they need to decide how this is best rendered in their target text. Recent publications are now beginning to attend to the notion of deliberateness in metaphor translation, and are revealing new questions and answers.
One stunning finding that has not been given much attention is the following. Most metaphors are limited to one (or occasionally just a few) words within the boundaries of a clause or sentence or utterance. However, some metaphors deliberately spill over between these linguistic boundaries and form more extended figurative textual structures and patterns (Textual patterning of metaphor | 24 | The Routledge Handbook of Metaph). This may even lead to whole paragraphs or bigger sections of text as constituting source and target domain expressions of metaphor which as such function as part of stories or arguments. Analytical and behavioural research still need much more work to come to terms with these phenomena to capture deliberate and non-deliberate (and related aspects of) metaphor use in discourse.
In discourse metaphors are not just expressed as words about a source domain in relation to some target domain. They can also be presented in the form of visual or multimodal metaphors. In such metaphors, source-domain elements usually work as source-domain referents that cannot be ignored by the receiver. This makes a lot of visual and multimodal metaphor deliberate.