Martin (1992: 214):
Turning from reformulation to comparison, the concern of internal comparative relations is not with fine tuning a meaning that has just been made but with noting similarities in lines of argument or interpretation.
This confuses conjunctive cohesion, the general non-structural resource for making textual transitions, with the more specific subtype: internal conjunctive relations — textual relations that are internal to the communication situation itself.
The distinction between internal and external relations is made in temporal cohesive conjunction, where it is the distinction between the temporal unfolding of the discourse (interpersonal time) and the temporal sequence of the processes referred to (experiential time), respectively (Halliday & Matthiessen 2004: 545).
In the case of logical relations between clauses, the distinction between internal and external relations is the distinction between the beta clause relating to the enactment of the proposition (interpersonal meaning) of the alpha clause and the beta clause relating to the figure (experiential meaning) that the alpha clause represents (Halliday & Matthiessen 2004: 419).