THE DISCOURSE FUNCTIONS OF THE PROGRESSIVE
The Progressive presents an ongoing event as something directly observed in relation to some point in time. This is either explicitly mentioned, as in 1 and 2 or else inferred as coinciding with speech time, 3:
1 By the end of January 1919 the main outlines of the peace settlement were emerging. (Paris 1919)
2 At half-past five, crowds were pouring into the subways.
3 What are you doing? I’m switching on the answer-phone. (coincides with speech time)
Progressive aspect provides a frame within which another event takes place. That is to say, the time-frame of the progressive event includes the bounded event:
We finally reach the supermarket and they are just closing the doors.
When they awoke, the frost was melting on the window and freezing into thin sheets of ice over the cold glass.
The girls were wearing their school uniforms when they came to my house.
(temporary state framing bounded event in simple past ‘came’)
Two simple forms, by contrast, are normally interpreted as a sequence:
We finally reach the supermarket and they close the doors.
Crowds poured into the subways and boarded the trains.
