Martin (1992: 447):
Finally, it needs to be kept in mind that the discussion of strings, chains, Themes and conjunctive relations has to this point focussed experientially on topical Themes. Theme selection however is also an important interpersonal resource …
 This is potentially misleading. A focus on topical (experiential) Themes is a textual focus, not an experiential focus. A topical Theme is the textual highlighting of experiential wording by means of the thematic structure of the clause.
 In SFL theory, theme selection is a resource of the textual metafunction, not the interpersonal metafunction. This is true for all Themes — textual, interpersonal and experiential (topical). The system of theme selection is set out in Halliday & Matthiessen (2004: 80; 2014: 106).